Add a pre-commit hook to check whether API docs are updated

[oandregal]

This PR is an alternative to #18657 Instead of automatically adding files to the commit (which could be problematic) this goes the route of checking whether the API docs are unstaged: if so, the commit will be prevented and the user has the choice of either adding them to the commit or skipping the check.

Test instructions

• Edit the JSON comment of an exported entity in packages/core-data/src/actions.js
• git add packages/core-data/src/actions.js
• git commit -m 'testing'

The expected result is that you can't commit due to the unstaged README files that were auto-updated due to the code change and will see a message like:

[aduth]

What would need to be done to reconcile this with #18840, notably that I've removed the explicit list of packages in that pull request.

[oandregal]

I'm fine with whatever approach that gets both shipped fast. It looks like this PR makes less changes to update-readmes so it could land first and then #18840?

[oandregal]

This needs to take also into account potential changes to handbook's API docs as well. Updated the testing instructions to reflect that.

Update: done this at 14f3a3b

[aduth]

Was it intentional to downgrade? I would expect it would need corresponding changes to package-lock.json if intended.

[oandregal]

I need to revert this.

For context: when we updated husky from 0 to 3 we introduced a breaking change: the git version required to work with husky is >= 2.13.2. Git hooks won't be executed in versions below. The git version bundled with my OS is lower than that, so I can't run the hooks (and test this change), so I had to downgrade it for testing.

I asked in core-editor about this change and it doesn't seem a widespread issue. Wasn't able to pin down easily the git versions that come with the supported OS for Windows and Mac to gauge how many could be affected. I guessed another way to look at it was that if people don't complain about hooks not executing for them, it's not an issue.

[oandregal]

31378db