Add launcher for the documentation in the menus
_Originally created by @alant on [#6767 (Redmine)](https://public-redmine-archive.tails.boum.org/code/issues/6767)_
This would solve tails/tails#5374 and be a better fix for tails/tails#5511
Feature Branch: bugfix/tails-documentation-launcher
### Related issues
- **Blocks** tails/tails#5374
issue