I know this post is about adding that feature to this app but if you have the link for the gif you want (or if you can copy the gif link from the search you are talking about you can add it as a link and make it appear in line with an !
Usually a link is formatted like this (without the spaces):
[ ] ( link )
If you add an ! at the beginning it'll post the image link inline within the comments like this (again minus the spaces):
! [ ] ( link )
I know this isnt what you asked for but in case it is helpful I thought I'd mention in as a stop gap for you :)