Migrate to Material Design 3

Hey, first of all thank you for maintaining that awesome app, it's my favorite PDF reader, due to its feature richness and intuitive user experience!

I do very like the new Material Design 3 and thought it would be awesome to see MJ PDF using it, therefore I took some time and migrated it to Material Design 3. You can find some screenshots below. When using Android 12 or up, the app's theme colors automatically adapt to the wallpaper. On lower Android versions, we use a Material 3 Theme Builder generated theme based on the previous app theme's primary/accent colors.

If you have any questions or concerns about the changes, feel free to ask about it :) I'm sorry for not having opened an issue earlier, I probably should have done that first but now it's too late already. I hope it's fine this way too.

I must admit I'm not really familiar with Gitlab, so I might be slow to respond as I'm not using it often (I hope I'll get automatic emails from Gitlab). Thanks for your time!