Automate generation of README values documentation

[colearendt]

Is your feature request related to a problem? Please describe.
As discussed in #80 , keeping values.yaml in sync with README.md can be tricky. As a result, a tool called helm-docs has been developed that uses go-templating to auto-generate the README.md

Describe the solution you'd like
Use GitHub Actions / CI to auto-generate helm-docs output / keep the README.md documentation up to date with values.yaml

Describe alternatives you've considered
Manual maintenance as is currently done

Additional context
I have started on an implementation of this, which has generated some questions:

• couchdb-helm currently displays "selections" of values. i.e. "these values are for XYZ, these are for ABC". Is this desirable to maintain? helm-docs does not currently support this idea, but I have created an issue to track doing so, because it seems nice
  • Unfortunately, if this is desirable, the workaround is a little gross in the short term. I am happy to PR for review based on preference of output
  • An example display of "all values in a big table together" is here
• Currently the documentation in README.md is quite concise (i.e. one sentence) and docs in values.yaml are quite thorough. If auto-generating, is it OK for README.md to become more verbose in line with values.yaml?

[colearendt]

Added #82 for discussion on the implementation path