Improve User Sign-in Flow

**Is your feature request related to a problem? Please describe.**
Our enterprise/EMU user sign-in flow currently involves multiple email/password login attempts before falling back to SSO. This has caused users to abandon the plugin without trying it and/or message GitHub admins for assistance.

**Describe the solution you'd like**
Present the user with a 'sign-in' picker with options for GitHub credentials, SSO, etc. rather than the current try/fail workflow.

**Additional Context**
Extension version: Actions - 0.25.8