Generate docs for only the staged/changed model(s)

[astro30]

Describe the feature you'd like
Be able to generate documentation only for the staged model(s).

Additional context
On big code bases, dbt docs generate could be extremely long (several minutes). When you have to run a particular hook, let's say check-model-has-all-columns, you have to execute dbt run and dbt docs generate before (it is a prerequisite). So, we can imagine to succession of hooks:

- repo: https://github.com/dbt-checkpoint/dbt-checkpoint
  rev: v1.2.0
  hooks:
    - id: dbt-run
    - id: dbt-docs-generate
    - id: check-model-has-all-columns

dbt-run will default to run only changed files. But dbt-docs-generate will not, that is why, I want to add this feature. This will streamline "doc-related" hooks for big codebases.

[pgoslatara]

@astro30 Feel free to add this feature!

[astro30]

Working on it ;)

[astro30]

I have suggested a PR here -> #210