Review FF release notes from FF69 to latest (FF75)

Release Notes: https://www.mozilla.org/en-US/firefox/releases/ Developer release notes: https://developer.mozilla.org/en-US/docs/Mozilla/Firefox/Releases

Also, diff prefs.js between latest and esr 68.

Also look at the bugs from 69 to 75 (update target_milestone param for each version)

Mozilla fixed: ​https://bugzilla.mozilla.org/buglist.cgi?product=Core&query_format=advanced&resolution=FIXED&target_milestone=mozilla69&order=priority%2Cbug_severity&limit=0

Mozilla reponed: https://bugzilla.mozilla.org/buglist.cgi?resolution=---&query_format=advanced&product=Core&target_milestone=mozilla69

Firefox fixed: ​https://bugzilla.mozilla.org/buglist.cgi?product=Firefox&query_format=advanced&resolution=FIXED&target_milestone=Firefox%2069&order=priority%2Cbug_severity&limit=0