Review for French spelling dictionary by Sorin Pos
Rated 3 out of 5 stars
The supported versions seem to be until Firefox 50, so the "Install add-on" button is disabled in Firefox 51.
Is this add-on not supported in Firefox 51?
Or do you simply need to update the plugin meta-data to extend it to be available in Firefox 51?
To create your own collections, you must have a Mozilla Add-ons account.