Mastodonplus.py/DEVELOPMENT.md

Here's some general stuff to keep in mind, and some work that needs to be done

• Mastodon.py tries to work for python2 as well as python3, so avoid things like annotations, use requests over urllib, et cetera.

• Current TODOs (2.3 support):

  • Add support for media updating
  • Add support for focal points
  • Add support for idempotency keys
  • Document error handling better