Libraries: Use default constructors/destructors in LibMarkdown

https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#cother-other-default-operation-rules

"The compiler is more likely to get the default semantics right and
you cannot implement these functions better than the compiler."

Userland/Libraries/LibMarkdown/Block.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2019-2020, Sergey Bugaev <bugaevc@serenityos.org>
+ * Copyright (c) 2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -15,7 +16,7 @@ namespace Markdown {
 
 class Block {
 public:
-    virtual ~Block() { }
+    virtual ~Block() = default;
 
     virtual String render_to_html(bool tight = false) const = 0;
     virtual String render_for_terminal(size_t view_width = 0) const = 0;

Userland/Libraries/LibMarkdown/BlockQuote.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2021, Peter Elliott <pelliott@serenityos.org>
+ * Copyright (c) 2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -18,7 +19,7 @@ public:
         : m_contents(move(contents))
     {
     }
-    virtual ~BlockQuote() override { }
+    virtual ~BlockQuote() override = default;
 
     virtual String render_to_html(bool tight = false) const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;

Userland/Libraries/LibMarkdown/CodeBlock.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2019-2020, Sergey Bugaev <bugaevc@serenityos.org>
+ * Copyright (c) 2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -21,7 +22,7 @@ public:
         , m_style(style)
     {
     }
-    virtual ~CodeBlock() override { }
+    virtual ~CodeBlock() override = default;
 
     virtual String render_to_html(bool tight = false) const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;

Userland/Libraries/LibMarkdown/CommentBlock.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2021, Ben Wiederhake <BenWiederhake.GitHub@gmx.de>
+ * Copyright (c) 2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -19,7 +20,7 @@ public:
         : m_comment(comment)
     {
     }
-    virtual ~CommentBlock() override { }
+    virtual ~CommentBlock() override = default;
 
     virtual String render_to_html(bool tight = false) const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;

Userland/Libraries/LibMarkdown/ContainerBlock.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2021, Peter Elliott <pelliott@serenityos.org>
+ * Copyright (c) 2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -23,7 +24,7 @@ public:
     {
     }
 
-    virtual ~ContainerBlock() override { }
+    virtual ~ContainerBlock() override = default;
 
     virtual String render_to_html(bool tight = false) const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;

Userland/Libraries/LibMarkdown/Heading.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2019-2020, Sergey Bugaev <bugaevc@serenityos.org>
+ * Copyright (c) 2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -23,7 +24,7 @@ public:
     {
         VERIFY(m_level > 0);
     }
-    virtual ~Heading() override { }
+    virtual ~Heading() override = default;
 
     virtual String render_to_html(bool tight = false) const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;

Userland/Libraries/LibMarkdown/HorizontalRule.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -16,10 +17,8 @@ namespace Markdown {
 
 class HorizontalRule final : public Block {
 public:
-    HorizontalRule()
+    HorizontalRule() = default;
-    {
+    virtual ~HorizontalRule() override = default;
-    }
-    virtual ~HorizontalRule() override { }
 
     virtual String render_to_html(bool tight = false) const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;

Userland/Libraries/LibMarkdown/List.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2019-2020, Sergey Bugaev <bugaevc@serenityos.org>
+ * Copyright (c) 2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -22,7 +23,7 @@ public:
         , m_start_number(start_number)
     {
     }
-    virtual ~List() override { }
+    virtual ~List() override = default;
 
     virtual String render_to_html(bool tight = false) const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;

Userland/Libraries/LibMarkdown/Paragraph.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2019-2020, Sergey Bugaev <bugaevc@serenityos.org>
+ * Copyright (c) 2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -20,7 +21,7 @@ public:
     {
     }
 
-    virtual ~Paragraph() override { }
+    virtual ~Paragraph() override = default;
 
     virtual String render_to_html(bool tight = false) const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;

Userland/Libraries/LibMarkdown/Table.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, the SerenityOS developers.
+ * Copyright (c) 2020-2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -31,8 +31,8 @@ public:
         RecursionDecision walk(Visitor&) const;
     };
 
-    Table() { }
+    Table() = default;
-    virtual ~Table() override { }
+    virtual ~Table() override = default;
 
     virtual String render_to_html(bool tight = false) const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;

Userland/Libraries/LibMarkdown/Text.h

@@ -1,6 +1,7 @@
 /*
  * Copyright (c) 2019-2020, Sergey Bugaev <bugaevc@serenityos.org>
  * Copyright (c) 2021, Peter Elliott <pelliott@serenityos.org>
+ * Copyright (c) 2022, the SerenityOS developers.
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -25,7 +26,7 @@ public:
         virtual size_t terminal_length() const = 0;
         virtual RecursionDecision walk(Visitor&) const = 0;
 
-        virtual ~Node() { }
+        virtual ~Node() = default;
     };
 
     class EmphasisNode : public Node {