added 1 version of all sprites, cutting sprites, and hide cursor

[lesleyrs]

Issue #, if available: closes https://github.com/jjant/runty8/issues/16, closes #18 (not related but look here https://github.com/jjant/runty8/pull/38#issuecomment-1409731204)

Description of changes: Added 1 version of all missing assets, I'm pretty confident they are all correct. The tool sprites are mostly 7x7 and the menu sprites at top are 6x6. For some reason the tool sprites are currently using 2 sprites though. Also there is a bug where if you save on a non-black sprite it moves down 1 row.

I also had to remove the .ppm files as they wouldn't update with the last updates you did so they went out of sync, not sure what happened there?

https://github.com/jjant/runty8/issues/16#issuecomment-1409735816 as I said over there, the spritesheet needs to be cleaned up a bit but ctrl-x is missing right now. The cursor should also always be hidden and only show the sprite cursor when needed.

Just added a ctrl-x cut feature to rearrange/cleanup the spritesheet, check if I implemented it correctly as I'm still learning rust. And another commit to hide cursor icon, I wasn't sure where to put it so I just chose somewhere. Also re-added the new sprite you made as I started working on the spritesheet before using git pull then missed it sorry.

I made a new issue that lists all of the above to quickly sum it up at https://github.com/jjant/runty8/issues/51

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[jjant]

Thank you!