Add support for `auto_merge` and `required_contexts`

[gjtorikian]

This PR extends the action to provide more configuration options when creating a deploy, by providing input support for auto_merge and required_contexts. More details can be found in the GitHub API docs: https://docs.github.com/en/rest/deployments/deployments?apiVersion=2022-11-28#create-a-deployment

auto_merge is fairly straightforward. It is currently defaulting to false, and we can preserve that in this change for backwards compatibility.

required_contexts, on the other hand, has three states:

1. ["test", "lint"], which is a specific list of contexts to run
2. [], which ignores all the contexts
3. undefined, which means, "run the default list of contexts"

Currently, required_contexts is set to []. In order to preserve backwards compatibility, users will have to pass an explicit "null" string for this input (supporting case 3). Omitting this input will skip all the required checks (case 2, the current case). Providing a multiline string covers case 1:

      with:
        required_contexts: |-
          test
          lint

[gjtorikian]

I had to change the inputs logic a bit here:

• "" or []: skip all required contexts
• "*": require all (default) contexts
• "test,lint": require thetestandlint` contexts

[bobheadxi]

Thanks for the contribution - if you're still interested in landing this, could you resolve the conflicts and remove the extraneous docs formatting changes? Thank you!

[gjtorikian]

Sure, I've done that, and run prettier.