Automatically synchronize photon assets with upstream photon design lib

[mcomella]

The canonical source for photon assets is here: https://github.com/FirefoxUX/photon-icons/ These get pulled into the android-components. However, sometimes changes are made in this repository on these assets that don't get reflected upstream, e.g. #766 and #778.

We should come up with a system that either:

• Prevents changes to these assets directly in this repository, encouraging users to contribute upstream (maybe a Danger check to add a warning if the photon module is modified?)
• Automatically synchronizes any changes in this repository to the photon assets upstream

┆Issue is synchronized with this Jira Task

[pocmo]

This is tracked "upstream" here:
FirefoxUX/photon-icons#23

[pocmo]

Note that photon-icons uses an automated process to generated the XML drawables while multiple of our icons are manually optimized to fix various issues.

[csadilek]

Moved to bugzilla: https://bugzilla.mozilla.org/show_bug.cgi?id=1793167

Change performed by the Move to Bugzilla add-on.