restructured extra directory

extra/templates/firefox/readme.md

@@ -0,0 +1,17 @@
+# Firefox
+
+1. Download the [template file](userChrome.css)
+
+2. Configure the template in `~/.config/clrsync/config.toml`:
+
+```toml
+[templates.firefox]
+enabled = true
+input_path = '~/.config/clrsync/templates/userChrome.css'
+output_path = '~/.mozilla/firefox/<profile>/chrome/userChrome.css'
+reload_cmd = ''
+```
+
+3. Enable `toolkit.legacyUserProfileCustomizations.stylesheets` in `about:config`
+
+4. Restart Firefox to apply the theme