Adding upstream version 5.2.3+dfsg.

Signed-off-by: Daniel Baumann <daniel@debian.org>

.github/workflows/docs.yml

@@ -0,0 +1,45 @@
+name: Docs
+
+on:
+  push:
+    branches-ignore:
+      - "dependabot/**"
+  pull_request:
+  workflow_dispatch:
+
+env:
+  FORCE_COLOR: 2
+  NODE: 16
+
+jobs:
+  docs:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Clone repository
+        uses: actions/checkout@v3
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v3
+        with:
+          node-version: "${{ env.NODE }}"
+          cache: npm
+
+      - run: java -version
+
+      - name: Install npm dependencies
+        run: npm ci
+
+      - name: Build docs
+        run: npm run docs-build
+
+      - name: Validate HTML
+        run: npm run docs-vnu
+
+      - name: Run linkinator
+        uses: JustinBeckwith/linkinator-action@v1
+        with:
+          paths: _site
+          recurse: true
+          verbosity: error
+          skip: "^(?!http://localhost)"