Add support for semantic highlighting

[yunti]

It's surpising how useful this is now I'm used to it.
https://twitter.com/intellijidea/status/844901295823585280

eg simple example, reason

vs js

[giraud]

interesting, but I don't know which version of Idea supports that feature.

[yunti]

The js screenshot is from intellij ultimate but this one is from pycharm, so it's probably supported throughout the platform.

[giraud]

it's a christmas tree... how can spot anything ? :)

[yunti]

Yup not the best example - but just wanted to show something quickly. In an actual editor it becomes must clearer very quickly and it's way faster to scan and pick out things.
And well, it's nearly christmas 🎄