ci: add build-docs workflow

Call the centralized reusable workflow from reqstool/.github to validate
Antora docs build cleanly on PRs and pushes to main.

Signed-off-by: jimisola <jimisola@jimisola.com>

Author: Jimisola Laursen

.github/workflows/build-docs.yml

@@ -0,0 +1,15 @@
+name: Build Docs
+on:
+  workflow_dispatch:
+  pull_request:
+    paths:
+      - "docs/**"
+  push:
+    branches:
+      - main
+    paths:
+      - "docs/**"
+
+jobs:
+  build:
+    uses: reqstool/.github/.github/workflows/build-docs.yml@main