[Feature] Reactions visualization

[johnsoncodehk]

Refs https://github.com/HalfdanJ/svelte-reactions, https://twitter.com/halfdanj/status/1658166562660941824

[rchl]

Just based on the gif it looks to me like the standard document highlight that just highlights references of the current variable.

Possibly in some other cases it does a bit extra but I feel like it could be easily confused for document highlights if implemented.

[mrleblanc101]

I think he is talking about the green line highlight and not the gray variable highlight.

[rchl]

Right, I see.

[johnsoncodehk]

Implement by https://github.com/volarjs/insiders/pull/5