GNOME Shell integration for Chrome version 8.2.1

Changes

• Firefox: show usefull error message instead of "Attempt to postMessage on disconnected port" in case native connector not installed.
• Fixed compatibility issue with Firefox 54+.

Known issues

• Version 8.2.1 source tarball is not published at ftp. Look to git branch "release/v8.2.1" for source code.

• Native host connector is not working in Google Chrome and Opera when installed via Debian Stretch or Sid repositories. To know "why?" look here, here and here. For a workaround look here.

• Web extension is broken on FreeBSD because of bug 212925.