Ladybird: Implement an AppKit chrome for macOS :^)

This adds an alternative Ladybird chrome for macOS using the AppKit
framework. Just about everything needed for normal web browsing has
been implemented. This includes:

* Tabbed, scrollable navigation
* History navigation (back, forward, reload)
* Keyboard / mouse events
* Favicons
* Context menus
* Cookies
* Dialogs (alert, confirm, prompt)
* WebDriver support

This does not include debugging tools like the JavaScript console and
inspector, nor theme support.

The Qt chrome is still used by default. To use the AppKit chrome, set
the ENABLE_QT CMake option to OFF.

Ladybird/CMakeLists.txt

@@ -81,6 +81,8 @@ if (ENABLE_QT)
     set(CMAKE_AUTORCC ON)
     set(CMAKE_AUTOUIC ON)
     find_package(Qt6 REQUIRED COMPONENTS Core Widgets Network Multimedia)
+elseif (APPLE)
+    find_library(COCOA_LIBRARY Cocoa)
 endif()
 
 set(BROWSER_SOURCE_DIR ${SERENITY_SOURCE_DIR}/Userland/Applications/Browser/)
@@ -124,11 +126,33 @@ if (ENABLE_QT)
         Qt/main.cpp
     )
     target_link_libraries(ladybird PRIVATE Qt::Core Qt::Gui Qt::Network Qt::Widgets)
+elseif (APPLE)
+    add_executable(ladybird MACOSX_BUNDLE
+        ${SOURCES}
+        AppKit/main.mm
+        AppKit/Application/Application.mm
+        AppKit/Application/ApplicationDelegate.mm
+        AppKit/Application/EventLoopImplementation.mm
+        AppKit/UI/Event.mm
+        AppKit/UI/LadybirdWebView.mm
+        AppKit/UI/LadybirdWebViewBridge.cpp
+        AppKit/UI/Tab.mm
+        AppKit/UI/TabController.mm
+        AppKit/Utilities/Conversions.mm
+        AppKit/Utilities/URL.mm
+    )
+    target_include_directories(ladybird PRIVATE AppKit)
+    target_link_libraries(ladybird PRIVATE ${COCOA_LIBRARY})
+    target_compile_options(ladybird PRIVATE
+        -fobjc-arc
+        -Wno-deprecated-anon-enum-enum-conversion # Required for CGImageCreate
+    )
 else()
     # TODO: Check for other GUI frameworks here when we move them in-tree
     #       For now, we can export a static library of common files for chromes to link to
     add_library(ladybird STATIC ${SOURCES})
 endif()
+
 target_sources(ladybird PUBLIC FILE_SET browser TYPE HEADERS
     BASE_DIRS ${SERENITY_SOURCE_DIR}/Userland/Applications
     FILES ${BROWSER_HEADERS}
@@ -205,9 +229,7 @@ function(create_ladybird_bundle target_name)
     endif()
 endfunction()
 
-if (ENABLE_QT)
-    create_ladybird_bundle(ladybird)
-endif()
+create_ladybird_bundle(ladybird)
 
 if(NOT CMAKE_SKIP_INSTALL_RULES)
     include(cmake/InstallRules.cmake)