Release 5.1.0 This release improves CSS for tab bar of the the non-ESR firefox, and fixes a typo in the user-agent rules. Thanks to Danny, Peter and Egor! Features: * Add ability to load a different theme based on the Firefox channel * tabmenu.css: Separate tabmenu.css for release 144+ * Makefile: Deploy release CSS Fixes: * Fix paths in makefile * Fix shared theme path * UserAgentManager: fix URL in the rule for Google Search