Remove bslint as dep. Install manually in workflows. Explain process in new CONTRIBUTING guide

[pinheadmz]

Closes #489

Removes bslint from dependencies and installs it manually in workflows process for CI testing.

Added a CONTIRBUTING.md guide to explain how to install and use bslint since it is not automatic anymore. While there, added sections about bmocha and commit message preferences.

Linked that from README and, while there, removed the short list of RPC commands that we don't maintain and just linked to the API docs.

[pinheadmz]

Installed on a fresh VPS:

 npm audit

                       === npm audit security report ===

found 0 vulnerabilities
 in 38 scanned packages

looks ok. npm run lint of course failed until I installed bslint manually, then lint test works. Looks like gtihub CI works as expected as well.

[coveralls]

Pull Request Test Coverage Report for Build 204024484

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.007%) to 58.983%

---

Totals
Change from base Build 202553015:	0.007%
Covered Lines:	19286
Relevant Lines:	30406

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💛 - Coveralls

[tuxcanfly]

OK.

[tynes]

ACK a3c34bc
Nit: some squashing could be useful

[pinheadmz]

rebase to 9fafb91:

Just squashin -- diff should be null