BrowserSettings: Create a BrowserSettings application :^)

Browser has a bunch of settings, but most are non-trivial to add here.
So far, these are implemented:

- Homepage URL
- Whether to close download windows when they complete

The others will be added in subsequent commits.

Userland/Applications/BrowserSettings/BrowserSettingsWidget.gml

@@ -0,0 +1,68 @@
+@GUI::Frame {
+    fill_with_background_color: true
+
+    layout: @GUI::VerticalBoxLayout {
+        margins: [10]
+        spacing: 5
+    }
+
+    @GUI::GroupBox {
+        title: "Homepage"
+        fixed_height: 70
+
+        layout: @GUI::VerticalBoxLayout {
+            margins: [16, 8, 8]
+            spacing: 2
+        }
+
+        @GUI::Widget {
+            layout: @GUI::HorizontalBoxLayout {
+                spacing: 16
+            }
+
+            @GUI::Label {
+                fixed_width: 32
+                fixed_height: 32
+                name: "homepage_image_label"
+            }
+
+            @GUI::Label {
+                text: "URL:"
+                text_alignment: "CenterLeft"
+                fixed_width: 30
+            }
+
+            @GUI::TextBox {
+                name: "homepage_url_textbox"
+                placeholder: "https://example.com"
+            }
+        }
+    }
+
+    @GUI::GroupBox {
+        title: "Downloads"
+        fixed_height: 70
+
+        layout: @GUI::VerticalBoxLayout {
+            margins: [16, 8, 8]
+            spacing: 2
+        }
+
+        @GUI::Widget {
+            layout: @GUI::HorizontalBoxLayout {
+                spacing: 16
+            }
+
+            @GUI::Label {
+                fixed_width: 32
+                fixed_height: 32
+                name: "download_image_label"
+            }
+
+            @GUI::CheckBox {
+                name: "auto_close_download_windows_checkbox"
+                text: "Automatically close download window when complete"
+            }
+        }
+    }
+}