Basic LSP implementation

[alexrp]

The syntax/semantic analysis APIs should now be sufficient for a basic LSP implementation. We don't need to be super ambitious here - just performing semantic highlighting would be a great first step.

Depends on:

• [x] #30
• [x] #86

[alexrp]

e2dbe09 implemented syntax classification.

Now we just need to hook up an LSP handler to our workspace and classification APIs.

[alexrp]

Depends on:

• [x] #78
• [x] #82