ci(docs): add Docusaurus build job

Standardise the docs-site build across the Sigilweaver suite. The
Cloudflare GitHub App handles deploy on push to main; this job
only verifies that `bun run build:cloudflare` succeeds on every
push and PR, matching the pattern already used by OpenProteo,
OpenQBW, OpenSQLAnywhere, OpenKSpace, and DICOM-Atlas.

Author: Nathan-D-R

.github/workflows/ci.yml

@@ -39,3 +39,18 @@ jobs:
 
       - name: cargo test
         run: cargo test --workspace --all-targets
+
+  docs:
+    name: Docs (Docusaurus)
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: docs
+    steps:
+      - uses: actions/checkout@v4
+      - uses: oven-sh/setup-bun@v2
+      - name: bun install
+        run: bun install --frozen-lockfile
+      - name: bun run build:cloudflare
+        run: bun run build:cloudflare
+