README: elaborate on registering the GitHub App

Now that I am trying to establish support for projects other than Git, I
need to register a new GitHub App. Let's document that process better
for the next person who wants to repeat that feat.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

README.md

@@ -91,4 +91,37 @@ As Webhook URL, the URL of the Azure Function was used, which can be copied in t
 
 The value stored in the Azure Function as `GITHUB_WEBHOOK_SECRET` was used as Webhook secret.
 
-The GitGitGadget GitHub app requires the following permissions: Read access to metadata, and Read and write access to checks, code, commit statuses, issues, pull requests, and workflows.
+The GitGitGadget GitHub app requires the following permissions: Read access to metadata, and Read and write access to Actions, Checks, Commit statuses, Contents, Issues, Pull requests, and Workflows. It needs the following webhook events to be enabled: Check run, Commit comment, Issue comment, Pull request, Pull request review, Pull request review comment, Push, Repository, and Status.
+
+#### Using `register-github-app-cli`
+
+A convenient alternative to clicky-clicky in the GitHub UI to register the GitHub is the convenient [`npx re
+gister-github-app-cli` command](https://github.com/gr2m/register-github-app-cli): Use it with `--org <owning-organization>` and a vari
+ation of this manifest:
+
+```yml
+name: <name>
+url: https://github.com/apps/<name>
+hook_attributes:
+  url: https://<function-app-name>.azurewebsites.net/api/GitGitGadget
+public: false
+default_permissions:
+  actions: write
+  checks: write
+  commit_statuses: write
+  contents: write
+  issues: write
+  metadata: read
+  pull_requests: write
+  workflows: write
+default_events:
+  - check_run
+  - commit_comment
+  - issue_comment
+  - pull_request
+  - pull_request_review
+  - pull_request_review_comment
+  - push
+  - repository
+  - status
+```