Add support for Tapbacks

This gives Spacebar the ability to decode SMS reaction tapback messages and associate them with the original message instead of displaying duplicated quoted messages for each reaction. This also gives Spacebar the ability to send tapback reactions.

![tapback1](/uploads/ee2d8925daa13ce5d895627532d098c8/tapback1.png)
![tapback2](/uploads/2be41ab99a83c6cd34d7d8f03d178a74/tapback2.png)