Document highlight should include identifiers just before cursor

[Kha]

When placing the cursor at the end of an identifier, we do not send out document highlights, which causes VS Code to serve its own, dumb highlights instead.

[Trace - 9:25:36 AM] Received response 'textDocument/documentHighlight - (579)' in 1ms.
Result: []

[david-christiansen]

While it does make sense to work around limitations in popular tools, this doesn't actually seem wrong to me. I'm also surprised when the thing that the cursor isn't pointing at lights up, though much less so than when random stuff spelled the same lights up!

Can/should we fix it on the VS Code side?

[david-christiansen]

(for clarity: when I say "the thing it isn't pointing at", its because the cursor is on the space after x in your screenshot, not on x)

[mhuisi]

We should match what VS Code does here on the language server side.