Issue/#860 Update README

[Askaholic]

Adds some more information about dev setup to the readme. Honestly this might be better placed in its own document at some point because it's getting quite extensive.

[codecov]

Codecov Report

Merging #869 (5618263) into develop (d24631c) will increase coverage by 2.27%.
The diff coverage is n/a.

❗ Current head 5618263 differs from pull request most recent head f518747. Consider uploading reports for the commit f518747 to get more accurate results

Impacted Files	Coverage Δ
server/rating.py	94.50% <0.00%> (ø)
server/metrics.py	100.00% <0.00%> (ø)
server/players.py	100.00% <0.00%> (ø)
server/exceptions.py	100.00% <0.00%> (ø)
server/ice_servers/nts.py	100.00% <0.00%> (ø)
server/timing/__init__.py	100.00% <0.00%> (ø)
server/message_queue_service.py	97.80% <0.00%> (ø)
server/ladder_service/violation_service.py
server/ladder_service/ladder_service.py
server/ladder_service/game_name.py
... and 33 more