[IMP]Mail: dyanimacally display of mail heading on basis of number of followers and allow to add more followers


Hello,
I have improved mail chatter If no other followers than the user, replace the current 'Followers of this document' text with a link 'Add followers' that duplicates the lightbox from 'Add others'.

More Details:
Task: https://www.odoo.com/web#id=9036&view_type=form&model=project.task&menu_id=3942&action=327
Pad: https://pad.odoo.com/p/r.qPG63jrJ3YLR5bEH

thanks
rba-odoo