Provide example of adding labels to entities using translatable

Author: natewiebe13

translation.rst

@@ -303,6 +303,11 @@ Sometimes you may want to create a message, but at the time of creation aren't
 sure how it would be translated. For example, it could be translated multiple
 times if intended to be displayed to multiple users.
 
+Using translatable objects also allows preparing translations without having a
+dependency on an entrypoint (such as a router) where the context for performing
+the translation is provided. For example, entities could prepare translatable
+strings (such as labels) without the need for a translator.
+
 Instead of translating a string at the time of creation, a ``Translatable``
 object can be created that can then be translated when used. Later this message
 can be translated with a translator in either PHP or in Twig.