Filament v3 support - drop filament v2 support - add laravel v11 support

[dinandmentink]

Drops filament v2 support and performs some related housekeeping.

Some notes:

• First 2 commits taken from Adds laravel 11 support #26 by @mateusjunges. 2 after that rewritten. I have no access to that branch so simply cherrypicked the commits.
• Filament introduces their own markdown editor based on EasyMDE, including file uploads: https://filamentphp.com/docs/3.x/forms/fields/markdown-editor. From what I see there are some cosmetic differences but almost complete feature parity. I might switch to the filamentphp default one for my own projects just to reduce a dependency.
• There is a clash resulting in double icons. I fixed this clash by specifically removing the mask-image set by filament. Alternatively it's possible to actually let filament do these font inclusions and simply remove the font awesome dependency. I opted to solve the clash as it is less dependent on filament's own markdown editor implementation.

All in all, if someone can upgrade to filament v3 with this dependency they could probably remove it and switch to the filament provided one. In most cases anyway.

[freekmurze]

Thanks!

[mateusjunges]

Thank you @dinandmentink! I didn't had the time to work on my PR.