Json: Add efficient copy and move constructors for Json{Array,Object}

This helps avoid copying JsonValues during parsing.

AK/JsonArray.h

@@ -10,6 +10,30 @@ public:
     JsonArray() {}
     ~JsonArray() {}
 
+    JsonArray(const JsonArray& other)
+        : m_values(other.m_values)
+    {
+    }
+
+    JsonArray(JsonArray&& other)
+        : m_values(move(other.m_values))
+    {
+    }
+
+    JsonArray& operator=(const JsonArray& other)
+    {
+        if (this != &other)
+            m_values = other.m_values;
+        return *this;
+    }
+
+    JsonArray& operator=(JsonArray&& other)
+    {
+        if (this != &other)
+            m_values = move(other.m_values);
+        return *this;
+    }
+
     int size() const { return m_values.size(); }
     bool is_empty() const { return m_values.is_empty(); }
 
@@ -18,6 +42,7 @@ public:
 
     void clear() { m_values.clear(); }
     void append(const JsonValue& value) { m_values.append(value); }
+    void append(JsonValue&& value) { m_values.append(move(value)); }
 
     String serialized() const;
     void serialize(StringBuilder&) const;

AK/JsonObject.h

@@ -11,6 +11,30 @@ public:
     JsonObject() { }
     ~JsonObject() {}
 
+    JsonObject(const JsonObject& other)
+        : m_members(other.m_members)
+    {
+    }
+
+    JsonObject(JsonObject&& other)
+        : m_members(move(other.m_members))
+    {
+    }
+
+    JsonObject& operator=(const JsonObject& other)
+    {
+        if (this != &other)
+            m_members = other.m_members;
+        return *this;
+    }
+
+    JsonObject& operator=(JsonObject&& other)
+    {
+        if (this != &other)
+            m_members = move(other.m_members);
+        return *this;
+    }
+
     int size() const { return m_members.size(); }
     bool is_empty() const { return m_members.is_empty(); }