Add a github output format

[thompson-tomo]

Introduction

I want to be able to easily see in github pr's any issues being introduced by the changes rather than having to read through the logs.

Proposal

Add a new output format github which logs issues following the github annotation format.

Describe the solution you'd like
Any violations/errors/issues should be reported as a github annotations making them easily visible.

References

See https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-commands#setting-a-warning-message for an example on the format the log messages expect.

[bendrucker]

https://github.com/terraform-linters/setup-tflint