feat: add Docker build for sphinx-latex image

.docker/sphinx-latex/Dockerfile

@@ -0,0 +1,23 @@
+FROM ubuntu:24.04
+
+LABEL org.opencontainers.image.source="https://github.com/nextcloud/documentation"
+LABEL org.opencontainers.image.description="Sphinx + LaTeX build environment for Nextcloud documentation"
+LABEL org.opencontainers.image.licenses="AGPL-3.0"
+
+ENV DEBIAN_FRONTEND=noninteractive
+
+RUN apt-get update \
+  && apt-get install -y --no-install-recommends \
+    make \
+    python3-pip \
+    latexmk \
+    tex-gyre \
+    texlive-fonts-extra \
+    texlive-fonts-extra-links \
+    texlive-fonts-recommended \
+    texlive-latex-extra \
+    texlive-latex-recommended \
+    texlive-xetex \
+    xindy \
+  && mktexlsr \
+  && rm -rf /var/lib/apt/lists/*

.github/dependabot.yml

@@ -17,3 +17,11 @@ updates:
     open-pull-requests-limit: 10
     cooldown:
       default-days: 10
+  - package-ecosystem: "docker"
+    directory: "/.docker/sphinx-latex"
+    schedule:
+      interval: "weekly"
+      time: "06:00"
+    open-pull-requests-limit: 10
+    cooldown:
+      default-days: 10

.github/workflows/docker-build.yml

@@ -0,0 +1,55 @@
+name: Build and publish sphinx-latex Docker image
+
+on:
+  push:
+    branches:
+      - master
+    paths:
+      - ".docker/sphinx-latex/**"
+  pull_request:
+    paths:
+      - ".docker/sphinx-latex/**"
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  packages: write
+
+jobs:
+  build-and-push:
+    name: Build and push sphinx-latex image
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@b5ca514318bd6ebac0fb2aedd5d36ec1b5c232a2 # v3.10.0
+
+      - name: Login to GitHub Container Registry
+        if: github.event_name != 'pull_request'
+        uses: docker/login-action@74a5d142397b4f367a81961eba4e8cd7edddf772 # v3.4.0
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata for Docker
+        id: meta
+        uses: docker/metadata-action@902fa8ec7d6ecbf8d84d538b9b233a880e428804 # v5.7.0
+        with:
+          images: ghcr.io/${{ github.repository }}/sphinx-latex
+          tags: |
+            type=raw,value=latest,enable={{is_default_branch}}
+            type=sha,prefix=sha-
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@14487ce63c7a62a4a324b0bfb37086795e31c6c1 # v6.16.0
+        with:
+          context: .docker/sphinx-latex
+          push: ${{ github.event_name != 'pull_request' }}
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=registry,ref=ghcr.io/${{ github.repository }}/sphinx-latex:latest
+          cache-to: type=inline