docs: generate kubectl plugin docs

[cronik]

add new make plugin-docs command that generates kubectl plugin docs to
docs/generated. a new navigation item is added under the 'Kubectl Plugin'
section that points to generated docs.

closes #327

[codecov]

Codecov Report

Merging #422 into master will not change coverage by %.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #422   +/-   ##
=======================================
  Coverage   84.28%   84.28%           
=======================================
  Files          70       70           
  Lines        6667     6667           
=======================================
  Hits         5619     5619           
  Misses        761      761           
  Partials      287      287           

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[dthomson25]

LGTM! This is awesome!

[dthomson25]

Unless you have any other changes, I'll merge it in!

[cronik]

@dthomson25 I wasn't sure exactly how the docs were built and published. That process now requires an additional step of "make plugin-docs", if that's something I can update let me know.

[dthomson25]

The docs are published by running mkdocs gh-deploy, but it makes a git commit so only committors can run it.

[cronik]

I added a new make target to release-docs which will generate the docs before running the gh-deploy.

[dthomson25]

@cronik I noticed that the CI failed with

+ tee /tmp/test-results/go-test.out
Makefile:127: *** missing separator.  Stop.

Are you able to run make test locally?

[dthomson25]

Great CI is now passing! I'll merge it in unless you have any other changes you want!

[cronik]

no more changes, merge away.