Add option to search highlighted syntax in Dash

[readeral]

Dash is great for looking up what you need when you know the syntax keyword but can't remember it's specifics, but it's also great for helping with code review/tutorials/contributing to existing code to be able to search up a syntax term you don't know.

It would be great to have this option built into the vscode touchbar - so I've created a pull request to that end #39 It also includes an update to the readme about how to limit the existing vscode buttons to make more space for Nasc touchbar