Update Datadog logo img tag with class attribute

Author: goruha

README.yaml

@@ -10,7 +10,7 @@ description: |-
   <picture>
     <source media="(prefers-color-scheme: dark)" srcset="https://cloudposse.com/images/partners/datadog-white.svg"/>
     <source media="(prefers-color-scheme: light)" srcset="https://cloudposse.com/images/partners/datadog-purple.svg"/>
-    <img alt="Datadog" src="https://cloudposse.com/images/partners/datadog-purple.svg" align="right" width="40%"/>
+    <img class="datadog-logo" alt="Datadog" src="https://cloudposse.com/images/partners/datadog-purple.svg" align="right" width="40%"/>
   </picture>