Update CI

[XhmikosR]

• specify fail-fast: false
• update to actions/setup-node@v2
• fix indentation

[XhmikosR]

@jakubpawlowicz we should probably run at least one version on Windows too. And/or update the readme line that says tested on Linux, OS X, and Windows

[jakubpawlowicz]

Yes we should. I can no longer test on OS X so I've just removed that. Re tests on Windows we should set it up.

[XhmikosR]

You can test OS X and Windows with Actions just fine :)

The easy way would be to just run the whole thing on all OS'es, even though it might be redundant running 4 Node.js version x 3 OS'es = 12 Actions.

[jakubpawlowicz]

I wasn't aware Actions support it. I wouldn't mind running them on Node.js 14 on OS X and Windows and the rest of them on Linux. Thoughts?

[XhmikosR]

Sounds good to me. I'll see if I can put something together in the next days and if we have a solid workflow file you can backport it to clean-css too.

[jakubpawlowicz]

Thanks, much appreciated! 👍