Custom emojis: import/export functions documentation.

support/documentation/content/en/documentation/user/streamers/emojis.md

@@ -20,3 +20,23 @@ On the [channel configuration page](/peertube-plugin-livechat/documentation/user
 {{% livechat_label livechat_configuration_channel_emojis_desc %}}
 
 ![Channel configuration / Channel emojis](/peertube-plugin-livechat/images/channel_custom_emojis.png?classes=shadow,border&height=400px)
+
+### Import / Export
+
+On the channel configuration page, there are an "{{% livechat_label action_import %}}" and an "{{% livechat_label action_export %}}" button.
+The "{{% livechat_label action_export %}}" button generates a file than you can then import on another channel.
+
+You can also generate a file to import from any other source (for example you can import your Twitch custom emojis).
+The file must be a valid JSON file, using the following format:
+
+```json
+[
+  {
+    "sn": ":short_name",
+    "url": "https://example.com/image.png"
+  }
+]
+```
+
+The `sn` attribute is the short name code.
+The `url` attribute can be any image url than your browser can access, or a [Data URL](https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/Data_URLs) representing the file you want to import.