chore(docs): Add AWS docs meta tags (aws-powertools#2170)

* Add docs meta tags.

* Use full Powertools names.

Author: phipag

docs/overrides/main.html

@@ -6,3 +6,8 @@
   <strong>Click here to go to latest.</strong>
 </a>
 {% endblock %}
+
+{% block extrahead %}
+    <meta name="guide-name" content="Powertools for AWS Lambda (Java)">
+    <meta name="service-name" content="Powertools for AWS Lambda">
+{% endblock %}