It provides guidelines to fix the following issues:
- Script execution failed
* Remove old installations
* Reinstall
* Check the host-app is installed correctly
- PassFF is not working and takes 99% CPU
* Check the PATH variable
- Add a subsection title 'Linux, MacOS, * BSD' for clarity
- Add a link to the documentation of Firefox on NativeMessaging
- Add both manifest locations on OSX: Per-user & System-wide