Adding/Updating Descriptions for SEO

[fhennig]

Pages should have descriptions with 130 to 150 characters, describing what's on the page. The description gets shown in search results.

• Adding descriptions #662
• Add descriptions airflow-operator#503
• Add descriptions druid-operator#620
• Add descriptions and fix formatting demos#97
• Add descriptions hbase-operator#557
• Add descriptions hdfs-operator#580
• Add descriptions hive-operator#511
• Add descriptions kafka-operator#755
• Add descriptions nifi-operator#674
• Add descriptions spark-k8s-operator#463
• Add descriptions superset-operator#538
• Add descriptions trino-operator#641
• Add descriptions zookeeper-operator#856
• Add descriptions opa-operator#624
• Add descriptions commons-operator#279
• Add descriptions secret-operator#499
• Add descriptions listener-operator#223