Feature: Add action to find matching bracket

[jeremypw]

Builtin highlight matching brackets only works over a limited number of characters. This works over whole document, scrolls to match and checks whether indent is the same.

This action (but not accelerator) is now exposed in the document context menu

[zeebok]

Just one optional comment but looks good to me! Excited to make use of this feature!

[jeremypw]

I'd like to add extra functionality to find where the error occured if possible but that will have to wait for another PR. I'd also like to expose the shortcut somehow but the document context menu does not currently show accels. Again, another PR.

[zeebok]

I'd like to add extra functionality to find where the error occured if possible but that will have to wait for another PR. I'd also like to expose the shortcut somehow but the document context menu does not currently show accels. Again, another PR.

I wonder if adding a Cheat Sheet option in the gear menu that gives a bunch of helpful shortcuts and features is a decent enough way to expose it?