Add init for ImageRunner mode

[FriggaHel]

Proposed changes

Add init for ImageRunner.
Only support:

• Name
• Artifact downloads

Ouput:

➭ saucectl init
11:45:51 INF Start Init Command
? Select region: us-west-1
? Select framework: imagerunner
? Docker Image to use: ubuntu:latest
? Download artifacts: always

The following files have been created:
  .sauce/config.yml


Before running your tests, you need to set the following environment variables:
  - DOCKER_USERNAME
  - DOCKER_PASSWORD

➭

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Checklist

• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• I have updated the json schema (if appropriate)

Further comments