add support for virtual UI, useful for automated end-to-end tests

[senko]

This allows us to set up a test end-to-end run, with pre-scripted user inputs.

Config used for the demo (see below):

  "ui": {
    "type": "virtual",
    "inputs": [
      {
        "text": "example-project"
      },
      {
        "button": "example"
      }
    ]
  },

Demo

https://github.com/Pythagora-io/gpt-pilot/assets/3362/e024c37e-3306-4115-a228-9a6d3746fd35