Add changelog note

Author: henrymercer

CHANGELOG.md

@@ -6,6 +6,7 @@ See the [releases page](https://github.com/github/codeql-action/releases) for th
 
 - We have improved the CodeQL Action's ability to validate that the workflow it is used in does not use different versions of the CodeQL Action for different workflow steps. Mixing different versions of the CodeQL Action in the same workflow is unsupported and can lead to unpredictable results. A warning will now be emitted from the `codeql-action/init` step if different versions of the CodeQL Action are detected in the workflow file. Additionally, an error will now be thrown by the other CodeQL Action steps if they load a configuration file that was generated by a different version of the `codeql-action/init` step. [#3099](https://github.com/github/codeql-action/pull/3099) and [#3100](https://github.com/github/codeql-action/pull/3100)
 - We added support for reducing the size of dependency caches for Java analyses, which will reduce cache usage and speed up workflows. This will be enabled automatically at a later time. [#3107](https://github.com/github/codeql-action/pull/3107)
+- You can now run the latest CodeQL nightly bundle by passing `tools: nightly` to the `init` action. In general, the nightly bundle is unstable and we only recommend running it when directed by GitHub staff. [#3130](https://github.com/github/codeql-action/pull/3130)
 
 ## 3.30.3 - 10 Sep 2025