Add uninstall guide

UNINSTALL.md

@@ -0,0 +1,9 @@
+# Uninstallation guide
+
+To uninstall the extension, simply right click the icon and click "Remove from Chrome" (Chrome) or "Remove extension" (Firefox). Thats it!
+
+## Before you leave
+
+Please let us know if you are uninstalling because of a bug. Report all bugs to the [issue tracker](https://github.com/Andrews54757/FastStream/issues). New bugs are usually addressed in 1-2 days.
+
+#### Please report any bugs you notice! We won't know about it otherwise!