CLI: create temporary sb repro-next command that only degits repros

[yannbf]

Issue: N/A

What I did

Added a sb repro-next command which will use the new format of repros by just degitting templates from https://github.com/storybookjs/repro-templates-temp

Here's the initial prompt. It will read configurations coming from repro-config.yml:

And once done:

How to test

1. yarn build cli
2. refer to the CLI bin and run repro-next

• Is this testable with Jest or Chromatic screenshots?
• Does this need a new example in the kitchen sink apps?
• Does this need an update to the documentation?

If your answer is yes to any of these, please make sure to include it in your PR.