Updates Docker release README to reflect admin password requirements (#4395)

Signed-off-by: Darshit Chanpura <dchanp@amazon.com>

Author: DarshitChanpura

docker/release/README.md

@@ -91,6 +91,10 @@ Here are three example scenarios of using above variables:
      ```
      $ docker run -it -p 9200:9200 -p 9600:9600 -e "discovery.type=single-node" opensearchproject/opensearch:1.1.0
      ```
+     Note: For OpenSearch 2.12 and later, a custom password for the admin user is required to be passed to set-up and utilize demo configuration.
+     ```
+     $ docker run -it -p 9200:9200 -p 9600:9600 -e OPENSEARCH_INITIAL_ADMIN_PASSWORD=<strong-password> -e "discovery.type=single-node" opensearchproject/opensearch:2.12.0
+     ```
   * OpenSearch-Dashboards:
      ```
      $ docker run -it --network="host" opensearchproject/opensearch-dashboards:1.1.0
@@ -129,9 +133,17 @@ Here are some example scenarios of using above variables:
      ```
      $ docker run -it -p 9200:9200 -p 9600:9600 -e "discovery.type=single-node" opensearchproject/opensearch:<TAG>
      ```
+     Note: For OpenSearch 2.12 and later, a custom password for the admin user is required to be passed to set-up and utilize demo configuration.
+     ```
+     $ docker run -it -p 9200:9200 -p 9600:9600 -e OPENSEARCH_INITIAL_ADMIN_PASSWORD=<strong-password> -e "discovery.type=single-node" opensearchproject/opensearch:<TAG>
+     ```
 
 #### Scenario 2: Disable Performance Analyzer Agent Cli
   * OpenSearch:
      ```
      $ docker run -it -p 9200:9200 -p 9600:9600 -e "discovery.type=single-node" -e "DISABLE_PERFORMANCE_ANALYZER_AGENT_CLI=true" opensearchproject/opensearch:<TAG>
      ```
+     Note: For OpenSearch 2.12 and later, a custom password for the admin user is required to be passed to set-up and utilize demo configuration.
+     ```
+     $ docker run -it -p 9200:9200 -p 9600:9600 -e OPENSEARCH_INITIAL_ADMIN_PASSWORD=<strong-password> -e "discovery.type=single-node" -e "DISABLE_PERFORMANCE_ANALYZER_AGENT_CLI=true" opensearchproject/opensearch:<TAG>
+     ```