Achievements + Bug Fixes 3/22

Changelog:
- Changed some background networking code to make way for future multiplayer Dreams
- Made the main directory and the arcade directory prettier
- Made picross grid properly disappear when exiting out of it back to the arcade
- Fixed an issue where singleplayer Trivia score didn't reset after each match
- Fixed an issue where singleplayer Trivia, when played for points, wouldn't end when the target was reached.
- Made it so trivia doesn't repeat questions unless it runs out of unique questions
- Rewrote the code for Number Combo so it hopefully feels a bit better to play.
- Added a letter display to Word Guess to see all known wrong letters easily.
- Added achievements for all the MicroDreams, SimplyTrivia, and Backrooms.