Keyboard shortcut to change blocking modes #371

Prerequisites

• I verified that this is not a filter issue
  • Filter issues MUST be reported at filter issue tracker
• This is not a support issue or a question
  • Support issues and questions are handled at /r/uBlockOrigin
• I performed a cursory search of the issue tracker to avoid opening a duplicate issue
  • Your issue may already be reported.
• I tried to reproduce the issue when...
  • uBlock Origin is the only extension
  • uBlock Origin with default lists/settings
  • using a new, unmodified browser profile
• I am running the latest version of uBlock Origin
• I checked the documentation to understand that the issue I report is not a normal behavior

Description

Add keyboard shortcut to temporarily disable uBlock Origin or change modes.

A specific URL where the issue occurs

http://www.petit-bateau.us/women/l/600

Steps to Reproduce

1. Open uBlock Origin's popup UI
2. Allow 3rd party scripts & frames in local rules to temporarily downgrade from Medium to Easy Mode.

Expected behavior:

A keyboard shortcut to quickly allow 3rd party frames & scripts downgrade to Easy Mode when uBlock Origin is set to Medium.

Actual behavior:

Currently only 3 keyboard shortcuts can be set.

Your environment

• uBlock Origin version: 1.17.4
• Browser Name and version: Firefox Nightly 66.0a1 (2019-01-07) (64-bit)
• Operating System and version: MacOS 10.14