add basic readme

Signed-off-by: Rajat Jindal <[email protected]>

Author: rajatjindal

README.md

@@ -1,3 +1,31 @@
 # Spin Plugin Releaser
 
-This GitHub release action helps with automation of releasing Spin Plugins. 
+`spin-plugin-releaser` is a GitHub action (backed by a [Spin app](https://github.com/rajatjindal/spin-plugin-release-bot) deployed on Fermyon Cloud) that automates the update of plugin manifests in spin-plugins repo when a new version of your spin plugin is released. If a release is marked as a 'prerelease' in github, it will not be released to the spin-plugins index.
+
+To trigger `spin-plugin-releaser` you can use a github-action which sends the event to the bot.
+
+# Basic Setup
+
+- Make sure you have enabled github actions for your repo
+- Add a `.spin-plugin.json.tmpl` template file at the root of your repo. Refer to [cloud-plugin](https://github.com/fermyon/cloud-plugin) repo for an example.
+
+- To setup the action, add the following snippet after the step that publishes the new release and assets:
+  ```yaml
+  - name: Update new version in spin plugins repo
+    uses: rajatjindal/spin-plugin-releaser@main
+    with:
+      github_token: ${{ secrets.GITHUB_TOKEN }}
+      upload_checksums: true
+  ```
+
+# Inputs for the action
+
+| Key                | Default Value          | Description                                                                          |
+| ------------------ | ---------------------- | ------------------------------------------------------------------------------------ |
+| template_file | `.spin-plugin.json.tmpl`           | The path to template file |
+| upload_checksums | false           | uploads the checksums-<tagname>.txt file to the release |
+
+# Limitations of spin-plugin-releaser
+
+- only works for repos hosted on github right now
+- The first version of plugin has to be submitted manually, by plugin author, to the spin-plugins repo