Improve documentation & Capture mathematical thinking

[elmarti]

I wrote this 3/4 years ago and there's lots of geometry which i've since become unfamiliar with.

Acceptance Criteria

• Add documentation mechanism to make it easier to understand the thought processes around some of the mathsgetti*
• Decide whether to use swagger decorators or simple tsdoc

*A portmanteau of math and spaghetti that I just invented

[elmarti]

Fixed by https://github.com/elmarti/react-joystick-component/commit/fab12ae9ff653d0b97d0277b5b736cdb09b79eaa