- Added ui button, basic but also centers text automatically, IT IS SLOW
- IN PROGRESS: adding a drop down select box

- Created a menu to pause the game when pressing escape
- Created a basic ui_button, with color, padding and behavior
- Refactored state and renderer code, moved renderer into state

- Moved a lot of items into separate header files
- Still compiling everything as a single translation unit (but maybe a
  heavier translation unit [if that is possible])
- setup compile_flags, a way to use clangd without using a build system
- stuff like clangd and cmake don't work well with unity builds, so I
  avoid jumping through hoops