Add a README section about supported versions

Author: henrymercer

README.md

@@ -16,6 +16,19 @@ We recommend using default setup to configure CodeQL analysis for your repositor
 
 You can also configure advanced setup for a repository to find security vulnerabilities in your code using a highly customizable code scanning configuration. For more information, see "[Configuring advanced setup for code scanning](https://docs.github.com/en/code-security/code-scanning/creating-an-advanced-setup-for-code-scanning/configuring-advanced-setup-for-code-scanning)" and "[Customizing your advanced setup for code scanning](https://docs.github.com/en/code-security/code-scanning/creating-an-advanced-setup-for-code-scanning/customizing-your-advanced-setup-for-code-scanning)."
 
+## Supported versions of the CodeQL Action
+
+The following versions of the CodeQL Action are currently supported:
+
+- v3 (latest)
+- v2 (deprecated, support will end on December 5th, 2024)
+
+The only difference between CodeQL Action v2 and v3 is the version of Node.js on which they run. CodeQL Action v3 runs on Node 20, while CodeQL Action v2 runs on Node 16.
+
+To provide the best experience to customers using older versions of GitHub Enterprise Server, we will continue to release CodeQL Action v2 so that these customers can continue to run the latest version of CodeQL as long as their version of GitHub Enterprise Server is supported. For example CodeQL Action v3.22.11 was the first release of CodeQL Action v3 and is functionally identical to v2.22.11. This approach provides an easy way to track exactly which features are included in different versions by looking at the minor and patch version numbers.
+
+For more information, see ["Code scanning: deprecation of CodeQL Action v2."](https://github.blog/changelog/2024-01-12-code-scanning-deprecation-of-codeql-action-v2/).
+
 ## Troubleshooting
 
 Read about [troubleshooting code scanning](https://docs.github.com/en/code-security/code-scanning/troubleshooting-code-scanning).