I work on VS Code. The release notes are just markdown [0] that we render inside of the editor. The interactive playground on the welcome page is also just markdown [1] but we replace all the code blocks with embedded editors

We don't provide a standard way for extensions to show their own release notes but we do support showing users the CHANGELOG file on extension pages. We are also tracking allowing extensions to contribute their own playground sections [2]

[0]: https://raw.githubusercontent.com/Microsoft/vscode-docs/mast...

[1]: https://raw.githubusercontent.com/Microsoft/vscode/master/sr...

[2]: https://github.com/Microsoft/vscode/issues/20449