Fix permissions.

Make sure (hopefully!) that the docs workflow has the correct
permissions to deploy the website.

Author: gouttegd

.github/workflows/docs.yml

@@ -5,6 +5,11 @@ on:
     branches: [ "main" ]
   workflow_dispatch:
 
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
 jobs:
   build:
     runs-on: ubuntu-latest