Semantic Highlighter

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This one is a bit complicated. Currently I can think of two approaches:

1. With Define a vscode.executeSemanticHighlightProvider command microsoft/vscode#91375, get semantic highlighting results by running an e2e test that interacts with a real instance of VS Code (and its language servers).
2. Run VS Code in browser context: https://github.com/Microsoft/vscode/wiki/How-to-Contribute#run and use puppeteer to extract colors. This is kinda far-fetched, but this would mean we neither need to maintain an integration with vscode-textmate nor with the semantic highlighters.