Why has a one-man team figured this out with Nostur and other client devs can’t seem to do so? This feature has been in Nostur for many many months. It searches Tenor and then inserts the link to the gif you select into your post. 

https://image.nostr.build/945f63a64edf3aa46fd85ed45eb30f07131326ace2edace1989f8dbfc1532a10.jpg