Custos Release Improvements for 1.2

Based on the Release Candidate for Custis 1.1 release, here are some suggestions to improve:

1. Improve LICENSE and NOTICE file according to guidance on - https://infra.apache.org/licensing-howto.html
2. Organize a per-release documentation tab on the website or wiki
3. We can model it against other examples like airflow - https://airflow.apache.org/docs/apache-airflow/stable/index.html
4. Have a pointer to Custos release policy, something like - https://airflow.apache.org/docs/apache-airflow/stable/release-process.html

Review the LICENSE and NOTICE files against the Apache licensing guidance linked in the issue. Then inspect the current Custos website or wiki documentation and compare its release organization with the Airflow documentation and release-process examples. Done means the licensing files are updated and per-release documentation includes a clear pointer to the release policy.

Written by the indexing model from the issue text.