Added hovered link URL preview, and it even tries to evade the pointer, so if you're hovering a link in the bottom left corner, it'll jump into the right corner. And its appearance/disappearance it animated with nice smooth GTK CSS animations, and it of course follows dark mode.

That, and added/fixed more small things.

Like focus behavior between WebView / LocationEntry is now handled better (opened a new tab? focus the entry; entered an address? unfocus the entry, focus the web view), and Ctrl-L now works to focus the location entry while selecting the current address (for Ctrl-C, or for typing another address over it).

This is powered by the new LadybirdTab widget that represent contents of a single tab inside the AdwTabView. It primarily contains the LadybirdWebView inside a GtkScrolledWindow, but now some more things, too.

This will also be useful for implementing per-tab navigation history later on.