Document Dev Container definition release process

[philliphoff]

Add documentation to describe how new Dev Container definitions (and updates to existing ones) propagate to VS Code. (E.g. it looks like vscode-dev-containers releases are created periodically, which are then eventually picked up by a new release of the remote-containers extension. However, I don't see any notes about the general timelines involved, release schedules, etc.)

[Chuxel]

Good suggestion - we'll get that into CONTRIBUTING.md. To answer the question:

1. The vscode-dev-containers repo does ship with the VS Code extension currently. (There is a feature request to do this out-of-band: Update dev container definitions in extension more frequently / "out-of-band" vscode-remote-release#425)
2. The Remote - Containers extension ships into Stable on the same release cadence as VS Code itself using four week iterations. Here is the current VS Code iteration plan with dates, and then the additions for the remote extensions.
3. The Remote - Containers extension ships into Insiders as new features land during the iteration. This is not currently an automated daily release like VS Code itself.
4. If there is urgency for an update to the definitions outside of this release cycle, we can do one-off updates to Insiders and Stable as the need arises - particularly for Insiders.

That help? Normally this is every month, but there is not a December release because of holiday schedules.

[Chuxel]

Updated with 2bf5052. Let me know if you'd like to see anything else in the content to help clarify!

[philliphoff]

That's perfect, thanks!