Improve VS Code dark theme

[karlhorky]

Building on @kutyel's #7, I've consolidated the VS Code Dark and VS Code Dark Plus themes and improved on them.

It seems that some tokens are incorrectly being marked as plain (such as CSS declaration values), meaning that I cannot style them.

@kutyel, can I ask why you created two themes (Dark and Dark+) instead of just sticking with the best version of one? I've consolidated them into one file in this PR.

Demo: https://codesandbox.io/s/5x1mmwn9nx

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[karlhorky]

Oops looks like that screwed up the HTML tags, fixed some things in 9d45fb5.

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[karlhorky]

Also punctuation. Not ideal for the = and " tokens, but with the current tokenization we can't do much better than that. And the darker gray makes the tags and attributes stand out more visually.

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[kutyel]

LGTM, I only exported the default settings from vscode into this files, but it's true that it is far from perfect 😉 thanks for your improvements!

[karlhorky]

@kitten @kutyel I did an additional refinement of the original "VS Code Dark Plus" Prisma.js theme today, in case that is also applicable here (not sure if all the tokens are available in prisma-react-renderer yet!)

PrismJS/prism-themes#103