Marketplace Request: Allows extensions to be published to a beta channel

[CoenraadS]

Much like VSCode has its own Insiders build, that auto-updates and allows for a tight feedback loop with actual users, it would be nice if something similar was available for extension authors.

Currently the process is to get people to uninstall the current extension, and manually install a .vsix extension. I propose that a beta-tab is added to an installed extension, where users can simply switch to the beta-channel if they want.

Then authors may be able to simply publish with a command like vsce publish beta major/minor/patch

[CoenraadS]

Duplicate: #15756