Add feature to indicate unused imports

[spikespaz]

Recently this feature was added as a built-in to VS Code for several languages (namely JS). I think it would be really nice to have this for D as well. I don't know the codebase that well, but based on other similar features like unused variables, it seems like a feature that would be easy to implement. Maybe even a feature for any unused symbol.

[WebFreak001]

I tried to find out how they implemented it but couldn't really find anything about it. Do you have any idea which APIs are used to implement this?

It wasn't a major priority yet so I didn't do any massive research, just a quick peek in a few files and docs when it was new.

[spikespaz]

@WebFreak001 I looked around as well and could not find a way to exactly replicate the functionality of TS and JS. Those languages seem to be treated as first-class priority citizens in the editor. But couldn't you just add a squiggle underline (green or red) to the unused import the same way as unused variables?

As long as unused imports are a feature in DScanner, my guess is that you could re-use much of the code for unused variables.