Add CI for autogeneration of api docs on push to main

[mahalrs]

Closes #307

This change add CI for generating API docs. The CI will run make api-docs and will stage ./docs/api.md file. This file will only be staged if there are diffs. So, the CI is not going to make a commit if there aren't any changes to API docs. The commit user is "github-actions[Bot].

I have deleted the ./docs/api.md file so when merging this PR, CI will generate, commit, and push ./docs/api.md file automatically. In future, this CI will run on every push to main but will commit/push changes only if there are changes to API docs.

[mahalrs]

I tested this CI on a different repository and it works as expected. It commits changes only if there are diffs.

[codecov-commenter]

Codecov Report

Merging #310 (abd6b35) into main (e30ea47) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #310   +/-   ##
=======================================
  Coverage   23.40%   23.40%           
=======================================
  Files          12       12           
  Lines         782      782           
=======================================
  Hits          183      183           
  Misses        592      592           
  Partials        7        7           

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[nitishm]

Let's give it a shot 🤞

[mahalrs]

Let's give it a shot 🤞

Looks like we need to add GITHUB_TOKEN because CI push is getting rejected because it's protected branch.