Developer docs

[xaur]

We have a bunch of content that keeps being rehashed everytime our devs help with an integration.

Also, our dev facing material and social presence is very lacking as compared to rest of PR. This also give people reason to FUD when lots of news stories happen about ethics and morals and community and events but no stories about tech details and development.

Existing efforts:

• https://github.com/raedahgroup/dcrdevdocs
• there has been some work by nwops and others but it got stalled

Examples:

• https://bitcoin.org/en/developer-documentation
• https://btcinformation.org/en/developer-documentation
• https://bitcoincore.org/en/doc/

Related:

• Tech blog (#132)