Add an uninstall command

[apolopena]

Problem this feature will solve

Uninstalling gitpod-laravel-starter is too complicated and undocumented.
Automated production deployment systems would need to be updated each time a new version of gitpod-laravel-starter is released, this is not acceptable.

Background

See #211

Proposed Solution

See #211

Constraints and Assumptions

Alternatives or Workarounds

Additional context

Add any other context or screenshots about the feature request here.