Show preview version updates

[Dreamescaper]

Thanks for a great project!

It would be nice to support packages updates to preview versions. There are two cases:

• Showing package update when currently installed version is already preview. E.g. current version is "11.0.0-preview.6", and there is existing "11.0.0-preview.7" update. I suggest showing such updates automatically.
• Showidng package update when stable version is installed. E.g. current version is "10.6.0", and there is existing "11.0.0-preview.7" update. In such case it should be opt-in, and preview package update should be displayed only when explicitly requested.

[Nulifyer]

I thought it had preview updates in details

[Nulifyer]

See here, you can select a pre-release version if you wanted.