Merge pull request #19 from github/update-readme

Update README to prepare for open sourcing

README.md

@@ -1,10 +1,55 @@
-# GitHub Helm Charts
+# GitHub Sigstore Policy Controller Helm Charts
 
-This repository hosts GitHub owned helm charts.
-These charts are published to GHCR as OCI images. Each chart
-release is attested by the [Attest Build Provenance Action](https://github.com/actions/attest-build-provenance).
+This repository hosts the GitHub's [Policy Controller](https://github.com/github/policy-controller) Helm charts.
 
-## Cutting a new release
+The policy controller is an an admission controller built to enforce policies
+on a Kubernetes cluster.
+
+The Helm charts included in this repository are configured to enforce that
+images installed on a cluster have provenance attestations generated with the
+[Attest Build Provenance GitHub Action](https://github.com/actions/attest-build-provenance).
+
+The charts are published to GitHub Container Registry (GHCR) as OCI images. Each release is attested by
+the [Attest Build Provenance Action](https://github.com/actions/attest-build-provenance).
+
+You can verify these release with the `gh` CLI:
+```bash
+gh attestation verify \
+    oci://ghcr.io/github/policy-controller-helm/policy-controller:v0.9.0-github2 \
+    --owner github
+```
+
+## Installing the Charts
+
+You will need to install two charts. First, install the policy controller:
+
+```bash
+helm install policy-controller \
+    ghcr.io/github/policy-controller-helm/policy-controller \
+    --create-namespace --atomic --version v0.9.0-github2
+```
+
+The `--create-namespace` will create the release namespace if not present.
+The `--atmoic` flag will delete the installation if failure occurs. 
+
+Next, install the default GitHub policy to be used with policy controller:
+
+```bash
+helm install policy-controller-policies \
+    ghcr.io/github/policy-controller-helm/policies --set policy.enabled=true \
+    --set policy.organization=MYORG
+```
+
+By setting `policy.organization` to a specific organization, the policy
+controller will verify the workflow that signed an image's attestation is hosted
+in a repository within the specified organization.
+
+See [here](charts/policies/values.yaml) for a complete set of modifiable 
+policy chart values.
+
+## Maintainer Documentation
+
+### Cutting a New Release
 
 When you are ready to cut a new release for a given Helm chart