Autocomplete Implementation

[FastestMolasses]

Description

Adds first iteration of the autocomplete feature.

Related Issues

Checklist

• I read and understood the contributing guide as well as the code of conduct
• The issues this PR addresses are related to each other
• My changes generate no new warnings
• My code builds and runs on my machine
• My changes are all related to the related issue above
• I documented my code

Screenshots

[thecoolwinter]

That last I just pushed should fix build errors. Going to merge once tests are passing and it looks ready to go

[thecoolwinter]

Looks like there's some bug with either requesting completion items or filtering them. If I have a swift script like:

let string = ""
string.spl

The LSP isn't returning split as an option for completions. Super weird, going to investigate more before merging.

[thecoolwinter]

That last commi fixes the issue I mentioned. It turns out that language servers can opt-out of client-side filtering by setting the isIncomplete flag in the item response. This checks for that flag and disables filtering if it's detected.