Add README for GHA Workflow

.github/workflows/chart-rebuild.yaml

@@ -43,8 +43,6 @@ jobs:
 
           echo "Rebuilding index.yaml"
           scripts/rebuild.sh
-          echo "currently in $(pwd)"
-          cat index.yaml
 
       - name: Create Pull Request
         id: cpr

scripts/README.md

@@ -0,0 +1,21 @@
+# Rebuilding Index
+
+The Helm `index.yaml` is hosted on the `gh-pages` branch of this repo. If this
+index becomes out-of-sync with the releases, you can rebuild it by using a
+GitHub Actions Workflow.
+
+## Prerequisites
+
+- To use the `rebuild.sh` script with our workflow, the `rebuild.sh`
+  script must be checked in to the `gh-pages` branch. If you make any changes
+  to the script in this directory, make sure you also commit the same changes
+  to the `gh-pages` branch.
+- You must have permission to run GitHub Actions Workflows for this repo.
+
+## Running the Action
+
+- Navigate to
+  https://github.com/rstudio/helm/actions/workflows/chart-rebuild.yaml.
+- Use the `Run Workflow` button to run the workflow.
+- Review the Pull Request created by the workflow.
+- When approved, merge the Pull Request into the `gh-pages` branch.