fix(menu): improve menu accessibility

[averyjohnston]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Build (npm run build) was run locally and any changes were pushed
• Lint (npm run lint) has passed locally and any fixes were made for failures

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Issue: https://ionic.zendesk.com/agent/tickets/38343

What is the new behavior?

• Menu can be closed with Escape key
• Menu is focused on open and traps focus

Does this introduce a breaking change?

• Yes
• No

Other information

[liamdebeasi]

This is looking great so far! Left a few comments below.

[liamdebeasi]

Great job! Good to merge once the other things we discussed on Slack are completed.