Add keyboard shortcut for toggling annotations

[aaron-tdouble]

Why:

The Special Projects team recently released a feature that allows a user the ability to toggle all diff annotations via the a hotkey across all files, similar to the way that i does for comments.

This change adds the hotkey to the docs to increase exposure of this new ability.

Issue: https://github.com/github/special-projects/issues/89
Merged github PR: https://github.com/github/github/pull/171199

Closes [issue link] #3900

What's being changed:

Adding this hotkey entry:

Check off the following:

• I have reviewed my changes in staging. (look for the deploy-to-heroku link in your pull request, then click View deployment)
• For content changes, I have reviewed the Content style guide for GitHub Docs.

[welcome]

Thanks for opening this pull request! A GitHub docs team member should be by to give feedback soon. In the meantime, please check out the contributing guidelines.

[aaron-tdouble]

@Devilishhh thanks for the approval. The PR is still showing as needing at least one approval which is weird (since you obviously approved). What do I need to do in order to allow this to be merged?

[Devilishhh]

This needs to be merged

[Devilishhh]

@Devilishhh thanks for the approval. The PR is still showing as needing at least one approval which is weird (since you obviously approved). What do I need to do in order to allow this to be merged?

Needs to be merged by someone that is authorised to do so @aaron-tdouble

[janiceilene]

@aaron-tdouble Thanks so much for opening a PR and an issue! I'll get this triaged for writer review ⚡

In the future, could you open an issue in docs content? That'll give writers an opportunity to weigh in on what changes will be needed (that plan is outlined in https://github.com/github/docs-team/issues/340#issuecomment-769974718).

[janiceilene]

This change looks great!

[Devilishhh]

All good