Update README

README.md

@@ -1,2 +1,18 @@
-# bundle-audit-action
-Runs bundle-audit check --update and outputs results.
+# Bundle Audit Action
+
+This is a GitHub action that runs `bundle-audit check --update`, and then outputs some information about the results. It's designed to be used in conjection with other actions that do something with the results.
+
+See:
+- [bundle-audit-check-action](https://github.com/planningcenter/bundle-audit-check-action)
+- [bundle-audit-to-asana-action](https://github.com/planningcenter/bundle-audit-to-asana-action)
+
+## Inputs
+
+None.
+
+## Outputs
+
+| Name | Description |
+|:-:|:-:|
+| `has_vulnerabilities` | "true" or "false" depending on whether any vulnerabilities were detected |
+| `audit_output` | JSON-encoded string containing the vulnerability output |