add optional prerequisites

Author: Xiaoyun Ding

articles/java/migration/github-copilot-app-modernization-for-java-rearchitecture.md

@@ -35,6 +35,8 @@ Common re-architecture scenarios include:
 
 - Visual Studio Code with the [GitHub Copilot modernization](https://marketplace.visualstudio.com/items?itemName=vscjava.migrate-java-to-azure) extension installed.
 - A GitHub Copilot subscription. For more information, see [Copilot plans](https://github.com/features/copilot/plans?ref_product=copilot).
+- (Optional) [Python](https://www.python.org/downloads/) for building a knowledge graph, which gives the agent a clearer understanding of your project structure during the rewriting process. If Python isn't available, the knowledge graph step is skipped.
+- (Optional) [Docker Desktop](https://www.docker.com/products/docker-desktop/) for runtime validation. If Docker isn't available, the runtime validation step is skipped.
 
 ## Enable the re-architecture feature