Add filter for edit translation URL #69

Hi! It's me again trying to get more filters!

I know we can filter the edit new url (msls_admin_icon_get_edit_new filter) but I could't find a similar filter to for when a translation already exist. Would it be possible to add something similar to what's implemented here (https://github.com/lloc/Multisite-Language-Switcher/blob/master/includes/MslsAdminIcon.php#L180) but for the edit link?

Thanks!

P.S If you want be to do a quick PR with a solution, I can do it no problem!