The plugin "converts" Roundcube into a Progressive Web Application
which can be "installed" into user device's operating system.

This is proof-of-concept.


CONFIGURATION
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1. Replace images in `/assets` directory to your Company logo. Note, that some
images contain background and some are transpartent. This is to support various
operating systems and the way they use PWAs.

https://realfavicongenerator.net/ will help you with creating images automatically
and choosing some colors.

2. You can also modify `/assets/manifest.json` to your liking.

3. Enable the plugin in Roundcube configuration file.