update readme

Signed-off-by: Andrew Johnson <ajohnson@gocardless.com>

plugins/github-deployments/README.md

@@ -60,3 +60,33 @@ spec:
   owner: CNCF
   lifecycle: experimental
 ```
+
+### Self-hosted / Enterprise GitHub
+
+1. Add the `host` and `apiBaseUrl` to your `app-config.yaml`
+
+```yaml
+# app-config.yaml
+
+integrations:
+  github:
+    - host: 'your-github-host.com'
+      apiBaseUrl: 'https://api.your-github-host.com'
+```
+
+2. Pass the host into the `EntityGithubDeploymentsCard`
+
+```typescript
+// packages/app/src/components/catalog/EntityPage.tsx
+
+import { EntityGithubDeploymentsCard } from '@backstage/plugin-github-deployments';
+
+const OverviewContent = () => (
+  <Grid container spacing={3} alignItems="stretch">
+    // ...
+    <Grid item xs={12} sm={6} md={4}>
+      <EntityGithubDeploymentsCard host='your-github-host.com' />
+    </Grid>
+    // ...
+  </Grid>
+);