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/CMakeLists.txt

@@ -0,0 +1,16 @@
+serenity_component(
+    BrowserSettings
+    RECOMMENDED
+    TARGETS BrowserSettings
+)
+
+compile_gml(BrowserSettingsWidget.gml BrowserSettingsWidgetGML.h browser_settings_widget_gml)
+
+set(SOURCES
+    main.cpp
+    BrowserSettingsWidget.cpp
+    BrowserSettingsWidgetGML.h
+)
+
+serenity_app(BrowserSettings ICON app-browser)
+target_link_libraries(BrowserSettings LibGUI LibConfig LibMain)