build tools: add an eslint --fix Git precommit hook

[ntwb]

Description

This pull requests seeks to add a Git "precommit hook" so that the ESLint command eslint --fix is run against any JavaScript files staged for commit during git commit

How Has This Been Tested?

1. To test this PR, remove a semi-colon from a file, e.g /date.index.js and save the file
2. Stage the file change for commit git add date/index.js
3. Commit the change `git commit -m "Test ESLint Fix Precommit Hook"
4. Confirm that the semi-colon removed from date/index.js has been restored

The above can be seen in this shell screencast: https://asciinema.org/a/UXeTZyHbF3IbW6IhNU0cvrVcj

Screenshots (jpeg or gifs if applicable):

Types of changes

Build tooling change

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code has proper inline documentation.

p.s. The package-lock.json has also been regenareated from scratch, becasue, npm /shrug

[aduth]

Seems like a reasonable addition to the workflow 👍

[aduth]

I've found that this conflicts with patch/partial commits, at least those made via the GitHub Desktop client, presumably because git add will add all changes from the tested files, even though I'd already made only a partial selection to commit.

[ntwb]

@aduth Hmmm, I think it relates to this lint-staged issue:
• lint-staged/lint-staged#62
There's an active WIP PR, but it's doesn't look like landing in the short term
• lint-staged/lint-staged#75

Maybe we should drop this and revert until a solution for the above lands?