* 10614: Add pre-commit hook for including the MPLv2
Adds to Python, JS, SCSS, Jinja HTML, Fluent templates and shell scripts
Note that the order of application of the hooks is important - we want to add a missing license before we check the formatting of files
* 10614: Update MPLv2 comments on all templates to match standard format produced by pre-commit hook
* Updates existing MPLv2 text to use a https URL
* Amend a handful of Fluent templates that used a token instead of the string "Mozilla" - this standardised things; translation was not used or needed
* Add missing MPLv2 where needed
* Update three tests that regressed with these changes, above
* 10614: Update pre-commit config to not add MPL to JS libraries; Remove MPL from the four files which should not have had it
Steve Jalim