Support Lezer grammars with our output pipeline

[joshgoebel]

It'd be nice to be able to use Lezer for parsing paired with our output pipeline... this would allow users wishing to pay a higher download cost to get much improved support for some languages that require a more complex parsing engine.

References:

• Support Prism.js grammar parsing but use the Highlight.js HTML/theme pipeline #3619
• private __emitTokens API #3620
• https://lezer.codemirror.net/docs/guide/

[joshgoebel]

getStyleTags was added to make this easier!