dynamic splash screen support with pbsplash

pbsplash is a new tool for generating splash images at runtime, this avoids having to bake them into every device package, allowing us to support more resolutions and arbitrary messages. It also supports animations to make the booting experience just a little nicer. pbsplash is in general much more versatile, supporting svg fonts and being able to render any arbitrary svg image.

You can check out pbsplash here: https://git.sr.ht/~calebccff/pbsplash

Things to do before marking this MR as ready

• Don't hardcode font paths
• Config file - or is it fine to specify everything via cmdline args?
• Switch to getopt for arg parsing
• Write tests (hard requirement? nope)
• Get tfblib merged in alpine (https://gitlab.alpinelinux.org/alpine/aports/-/merge_requests/29853)
• Move pbsplash from sourcehut to gitlab not relevant anymore as discussed in chat

pbsplash needs YOUR help! give it a whirl on your postmarketOS edge device with the instructions here