Expand Airship 2.0 Developers Guide

[michaelfix]

As an operator, I need an Airship 2.0 Developers Guide, so that I can have a comprehensive reference site on how to contribute code to Airship 2, how to test, push, and merge changes to support development of feature functionality and resolving bugs within the Airship 2.0 components like airshipctl, treasuremap site types, SIP, ViNO, Image Builder, etc..

The effort involves updating and expanding the existing Developers Guide in the "Airship 2 Development" section of the Airship 2 Docs website.

[MichelleE-11]

Matthew Fuller (mf4192) confirmed both Developers guides below are current

Developers Guide : https://docs.airshipit.org/airshipctl/developers.html
Airship UI Developer's guide : https://docs.airshipit.org/airshipui/developers.html