Bring back unused variable highlight in JavaScript

[waderyan]

From @saharso on August 21, 2016 8:16

When I first started using vs code, There used to be a very useful green highlighting for variables that were declared, but not used throughout the code. This was very helpful with keeping my code clean and tidy. For some reason this feature was removed a few months ago. I can't see why. Please bring it back.

Sahar Soffer.

Copied from original issue: microsoft/vscode#10755

[waderyan]

From @alexandrudima on August 22, 2016 7:55

fyi @dbaeumer

[waderyan]

From @dbaeumer on August 22, 2016 8:35

@waderyan this is something the tsserver has to implement.
@saharso you can use a linter plugin (like eslint) to get that feature.

[DanielRosenwasser]

I'm going to close this as a duplicate of #10449.