ci: automate generation and publishing of docs

[miparnisari]

For #2508.

The goal of this PR is that every time we change the SpiceDB CLI, we create an automated PR against authzed/docs that updates the docs (https://authzed.com/docs/spicedb/concepts/commands)

NOTE: the workflow docs.yaml hasn't been tested yet! (nektos/act didn't work in my machine)

[codecov]

Codecov Report

❌ Patch coverage is 81.25000% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.42%. Comparing base (1248818) to head (9625334).

Files with missing lines	Patch %	Lines
pkg/cmd/root.go	83.88%	5 Missing and 5 partials ⚠️
cmd/spicedb/main.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2688      +/-   ##
==========================================
- Coverage   79.44%   79.42%   -0.02%     
==========================================
  Files         456      456              
  Lines       47322    47325       +3     
==========================================
- Hits        37592    37582      -10     
- Misses       6968     6976       +8     
- Partials     2762     2767       +5     

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