firefox: add extra flag options

also added note that profile selection is not available on windows

pages/common/firefox.md

@@ -27,6 +27,14 @@
 
 `firefox --headless --screenshot {{path/to/output_file.png}} {{https://example.com/}}`
 
-- Use a specific profile directory to allow multiple separate instances of Firefox to run at once:
+- Use a specific profile directory to allow multiple separate instances of Firefox to run at once (not available for Windows):
 
 `firefox --new-instance --profile {{path/to/directory}} {{https://example.com/}}`
+
+- Create a new profile in the default directory without starting Firefox:
+
+`firefox --CreateProfile {{profile_name}}`
+
+- Set Firefox as default browser:
+
+`firefox --setDefaultBrowser