Generate docs from code

[5chdn]

Similar to the JSON-RPC docs that are automatically generated in the CI, we want:

• chainspec parameters automatically documented
• config file parameters automatically documented

Whenever there is a change to code, ideally we have scripts that extract the docs from the code and push it to the wiki/config generator.

• https://github.com/paritytech/parity-config-generator
• https://github.com/paritytech/parity-ethereum/blob/master/scripts/gitlab/publish-docs.sh

[5chdn]

Follow-up to #8835

[jam10o-new]

#10067 I'm working on the config file side of this

[adria0]

Closing issue due to its stale state.