Add documentation for team approver

This feature is now tested and this PR adds the necessary documentation
to show how to implement org team expansion for approvers.

Signed-off-by: Thomas Stringer <thomas@trstringer.com>

README.md

@@ -38,6 +38,31 @@ steps:
 - `minimum-approvals` is an integer that sets the minimum number of approvals required to progress the workflow. Defaults to ALL approvers.
 - `issue-title` is a string that will be appened to the title of the issue.
 
+## Org team approver
+
+If you want to have `approvers` set to an org team, then you need to take a different approach. The default [GitHub Actions automatic token](https://docs.github.com/en/actions/security-guides/automatic-token-authentication#permissions-for-the-github_token) does not have the necessary permissions to list out team members. If you would like to use this then you need to generate a token from a GitHub App with the correct set of permissions.
+
+Create a GitHub App with **read-only access to organization members**. Once the app is created, add a repo secret with the app ID. In the GitHub App settings, generate a private key and add that as a secret in the repo as well. You can get the app token by using the [`tibdex/github-app-token`](https://github.com/tibdex/github-app-token) GitHub Action:
+
+```yaml
+jobs:
+  myjob:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Generate token
+        id: generate_token
+        uses: tibdex/github-app-token@v1
+        with:
+          app_id: ${{ secrets.APP_ID }}
+          private_key: ${{ secrets.APP_PRIVATE_KEY }}
+      - name: Wait for approval
+        uses: trstringer/manual-approval@v1.6.0-rc.2
+        with:
+          secret: ${{ steps.generate_token.outputs.token }}
+          approvers: myteam
+          minimum-approvals: 1
+```
+
 ## Timeout
 
 If you'd like to force a timeout of your workflow pause, you can specify `timeout-minutes` at either the [step](https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idstepstimeout-minutes) level or the [job](https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idtimeout-minutes) level.