Allow specifying a set of lines in the URL to be highlighted in the UI

[ribosomerocker]

Feature request

It's useful for emphasizing some parts of the code especially when people are asking for help. Similarly to how you can highlight a set of line in a URL via GitHub, like https://github.com/haskell/play-haskell/blob/master/hie.yaml#L9-L15

The UI for highlighting a URL could be similar to GitHub's, where it's different from text selection, and to highlight a single line you press on the line number on the left, and to highlight multiple lines you click on a line first then shift+click on a line to highlight the range of lines.

[tomsmeding]

I think this would be nice too, but the problem is that I'm using a pre-existing editor, called Ace. This editor doesn't seem to support something like this directly (see e.g. the configuration part of its manual).

Perhaps something can be cooked up as an Ace extension.