Cache ESLint and stylelint

[XhmikosR]

Generally it speed things up a lot. There are some cases like when changing rules that one needs to remove the cache, but other than that it should work fine.

Please test it out with your normal workflow.

[MartijnCuppens]

I tested the stylelint config and everything looked fine. I was a bit worried this config would conflict with the build-in linter from Webstorm, but everything looks ok.

However, we could gain some additional speed if we change the lint script to:
"lint": "npm-run-all --parallel js-lint-* css-lint-*",
This decreases the runtime from ~1.8s to ~1.4s on my machine
We can also change this on the other locations and maybe just remove the js-lint and css-lint scripts.

But we can maybe cover this in another PR if needed.

[MartijnCuppens]

Looks ok for stylelint (didn't test eslint too much)

[XhmikosR]

The comment about the individual scripts is a little unrelated to this patch. This is a very specific change.

What you describe it's in my TODO but I still want to have the wrapper script. It's a lot more convenient.

[Johann-S]

it seems faster to me 👍

[XhmikosR]

We'll see how this goes in the long term.