Add "Translate messages" section

Author: Programie

README.md

@@ -62,6 +62,26 @@ media:
 
 There are also some more options to restrict those downloads to specific file types, chats or limit them by size. For more options, have a look into the [config.sample.yml](config.sample.yml).
 
+## Translate messages
+
+It is possible to use the Telegram API to translate messages.
+
+You might specify the target language using the `translate_to_lang` property in your `config.yml`:
+
+```yaml
+translate_to_lang: "en"
+```
+
+Note: Use the two-letter ISO 639-1 language code (examples: "de", "en", "es", "it").
+
+The translated message will be written into `translated_text` which can be mapped to any field using the output map configuration in your `config.yml`:
+
+```yaml
+output_map:
+  "message.original": "message.text"
+  "message.translated": "translated_text"
+```
+
 ## Initial setup
 
 When started for the first time, the application will ask you to connect with your Telegram account.