Add ESLint and Stylelint caches to GitHub actions workflow

[colinrotherham]

During workflow runs we only need to lint "changed" files

Both ESLint and Stylelint support this 👍

Locally too, this will remove a 2-3 second delay during (future) git hook "lint" runs: https://github.com/alphagov/govuk-frontend/pull/2848

[colinrotherham]

Converting back to draft whilst we wait for https://github.com/stylelint/stylelint/pull/6356 🎉

[jeddy3]

Converting back to draft whilst we wait for https://github.com/stylelint/stylelint/pull/6356 🎉

We've just released [email protected] with this fix in. It also contains a new --cache-strategy content flag that you may want to use for parity with how you use ESLint.

[colinrotherham]

We've just released [email protected] with this fix in. It also contains a new --cache-strategy content flag that you may want to use for parity with how you use ESLint.

Thanks @jeddy3 (and @kimulaco @kaorun343 @ybiquitous)

Massively appreciate the new addition (and contribution) 🙌

[colinrotherham]

@36degrees This one's ready to review again 😊

Not a huge speed bump for the GitHub workflow, but noticeable when running gulp dev (touching lots of Sass files)