fix: create the PR according to our own standards (#34)

# Description

When we update the workflows with `update_workflows.sh` a PR is
automatically created. But the description of it didn't follow our own
template. This PR adds a multiline description with `Description` and
`Verification` section.

# Verification

None.

update-workflows.sh

@@ -52,7 +52,18 @@ function create_commit_and_pr() {
   git commit -m "update workflows to latest version"
   git push --set-upstream origin update-workflows
 
-  gh pr create --title "ci: update workflows to latest version" --body "" --base main
+  body=$(cat <<-EOF
+    # Description
+
+    This PR updates all workflows to the latest version.
+
+    # Verification
+
+    Done by the workflows in this feature branch, except for the release workflow.
+EOF
+  )
+
+  gh pr create --title "ci: update workflows to latest version" --body "$body" --base main
   gh pr view --web
 }