Document inputs (#9)

Intentionally omitting `initial-delay` as about to be removed in favour
of awaiting > 0 non-ignored jobs as a startup strategy. GitHub has been
observed in the past to take >1min to spawn job requests when it is
experiencing issues (aka nearly every day).

README.md

@@ -39,3 +39,14 @@ jobs:
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
 ```
+
+## Inputs
+
+| Name     | Description                                                                                                                            | Required | Default                                                     |
+|----------|----------------------------------------------------------------------------------------------------------------------------------------|----------|-------------------------------------------------------------|
+| token    | GitHub token to use to interact with the GitHub API, unless you have rate limit concerns this should be `${{ secrets.GITHUB_TOKEN }}`. | Yes      |                                                             |
+| ref      | Git reference to checkout. The default supports Pull Requests, Merge Queues as well as branch pushes.                                  | No       | `${{ github.event.pull_request.head.sha \|\| github.sha }}` |
+| interval | The number of seconds in between polls of the GitHub API for check run conclusions.                                                    | No       | `5`                                                         |
+| timeout  | The number of seconds before the job is declared a failure if check runs have not yet concluded.                                       | No       | `300`                                                       |
+| name     | The name of the Sloth's own check run. This is used to ensure Sloth does not wait upon itself.                                         | No       | `"sloth"`                                                   |
+| ignored  | A comma separated list of check run names to ignore when determining an overall result.                                                | No       | `""`                                                        |