slack -> discord link in readme

Changed to reflect new Ember Discord community link

Author: Jacob

README.md

@@ -15,7 +15,7 @@ You can view the most-upvoted feature requests with [this link](https://github.c
 
 ## Getting help
 
-Please open an issue or stop by #ec-addon-docs in Slack!
+Please open an issue or [join the Ember community on Discord]( https://discord.gg/zT3asNS )
 
 ## About