Summary:
This PR fixes https://github.com/facebook/flipper/issues/798 by adding customizable hotkeys to reload and/or open developer menu in React Native apps.
#### TODO:
- [x] Add correct icon for removing content of the hotkey input (currently using `undo`) - cc passy 😄
## Changelog
Add customizable hotkeys to reload and/or open developer menu in React Native apps.
Pull Request resolved: https://github.com/facebook/flipper/pull/822
Test Plan:
- Run React Native on version `0.62.0-rc.2` (you can use this app: https://github.com/lucasbento/RNWithFlipper);
- Open the Preferences window (`⌘,`);
- Customise the React Native hotkeys to whatever you want;
- Test them out with Flipper's window active and inactive.
> **Note**: this has been tested only in macOS.
Reviewed By: jknoxville
Differential Revision: D20061833
Pulled By: passy
fbshipit-source-id: 601d29e07d7de2683d2c70c7c87f0d841aa3559e
