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 👍

This removes a 2-3 second delay during both gulp dev file changes (Sass and JS files) and git hook "lint" runs

Before

GitHub Actions workflow

Lint:              13s
Test projects:     1m 25s
Screenshots:       1m 24s
Total:             3m 2s

npm run lint:js    4.87s user 0.44s system 141% cpu 3.752 total

npm run lint:scss  4.91s user 0.65s system 144% cpu 3.845 total

After

GitHub Actions workflow (~49s faster with Jest, ESLint and Stylelint caching)

Lint:              4s
Test projects:     1m 1s
Screenshots:       1m 8s
Total:             2m 13s

npm run lint:js    1.16s user 0.36s system 105% cpu 1.438 total

npm run lint:scss  2.41s user 0.56s system 137% cpu 2.173 total

[36degrees]

If we changed the stylelint config, will we need to clear the cache to force it to re-lint all files against the new config? I can't see anything in the stylelint docs to suggest this is handled for us.

(Same applies for eslint)

[colinrotherham]

ESLint automatically marks the cache as stale when the config changes

Let me check what StyleLint does (good shout)

Update: StyleLint doesn't yet but it's been picked up in stylelint/stylelint#2908 (comment)

[colinrotherham]

Converting back to draft whilst we wait for stylelint/stylelint#6356 🎉

[jeddy3]

Converting back to draft whilst we wait for stylelint/stylelint#6356 🎉

We've just released stylelint@14.13.0 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 stylelint@14.13.0 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)