Ladybird: Implement a JavaScript console for the AppKit chrome

This adds menu items to open an interactive JavaScript console for a web
page. This more or less mimics the Qt implementation of the console.
Hooks are included to tie the lifetime of the console window with the
tab it belongs to; if the tab is closed, the console window is closed.

Ladybird/AppKit/UI/TabController.mm

@@ -334,6 +334,8 @@ enum class IsHistoryNavigation {
 
 - (void)windowWillClose:(NSNotification*)notification
 {
+    [[self tab] tabWillClose];
+
     auto* delegate = (ApplicationDelegate*)[NSApp delegate];
     [delegate removeTab:self];
 }