Add :emoji settings to config.md

docs/config.md

@@ -486,3 +486,8 @@ config :ueberauth, Ueberauth,
     microsoft: {Ueberauth.Strategy.Microsoft, [callback_params: []]}
   ]
 ```
+
+## :emoji
+* `shortcode_globs`: Location of custom emoji files. `*` can be used as a wildcard. Example `["/emoji/custom/**/*.png"]`
+* `groups`: Emojis are ordered in groups (tags). This is an array of key-value pairs where the key is the groupname and the value the location or array of locations. `*` can be used as a wildcard. Example `[Custom: ["/emoji/*.png", "/emoji/custom/*.png"]]`
+* `default_manifest`: Location of the JSON-manifest. This manifest contains information about the emoji-packs you can download. Currently only one manifest can be added (no arrays).