Added client for emacs to the list of applications

Using-Mastodon/Apps.md

@@ -16,6 +16,7 @@ Some people have started working on apps for the Mastodon API. Here is a list of
 |Tooter|Chrome|<https://github.com/ineffyble/tooter>|[@effy@mastodon.social](https://mastodon.social/users/effy)|
 |tootstream|CLI|<https://github.com/magicalraccoon/tootstream>|[@Raccoon@mastodon.social](https://mastodon.social/users/Raccoon)|
 |[Mastodon UWP (beta)](https://github.com/woachk/mastodon/releases)|Windows 10|<https://github.com/woachk/mastodon>|[@my123@mastodon.social](https://mastodon.social/users/my123)|
+|[mastodon.el](https://github.com/jdenen/mastodon.el)|Emacs|<https://github.com/jdenen/mastodon.el>|[@johnson@mastodon.social](https://mastodon.social/users/johnson)|
 
 ## Bridges from/to other platforms