workflows: docs: add

Create a custom workflow for deploying our documentation to GitHub
Pages. This allows us to retain the original YAML-to-documentation
generation process we've used in the past, and stops us from relying
solely on files already being on the main branch for documentation build
and review.

We have to incorporate two new community actions for this:

1. `peaceiris/actions-gh-pages`, for deploying the actual docs using a
`gh-pages` branch (which will be created after the first merge to main)
2. `rossjrew/pr-preview-action`, for creating docs previews so we're
   able to review the changes before merge. Comments will be posted on
   the PR providing preview links.

AI-Generated: Uses Claude Sonnet 5

Signed-off-by: Trevor Gamblin <tgamblin@baylibre.com>

Author: threexc

.github/workflows/docs.yml

@@ -0,0 +1,85 @@
+# SPDX-FileCopyrightText: 2026 The RISE Project
+# SPDX-License-Identifier: MIT
+
+name: Build and deploy documentation
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - "docs/**"
+  pull_request:
+    types: [opened, synchronize, reopened, closed]
+  workflow_dispatch:
+
+concurrency:
+  group: docs-${{ github.ref }}
+
+jobs:
+  preview:
+    if: github.event_name == 'pull_request'
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        if: github.event.action != 'closed'
+        with:
+          python-version: '3'
+
+      - name: Install package doc generator dependencies
+        if: github.event.action != 'closed'
+        run: pip install -r docs/requirements.txt
+
+      - name: Generate package pages from YAML
+        if: github.event.action != 'closed'
+        run: python docs/packages/generate_packages_doc.py
+
+      - name: Build with Jekyll
+        if: github.event.action != 'closed'
+        uses: actions/jekyll-build-pages@v1
+        with:
+          source: ./docs
+          destination: ./_site
+
+      # Auto-detects deploy vs. removal from the pull_request event action,
+      # so this same step both publishes updates and tears down the preview
+      # when the PR is closed.
+      - name: Deploy or remove PR preview
+        uses: rossjrw/pr-preview-action@v1
+        with:
+          source-dir: ./_site
+
+  deploy:
+    if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3'
+
+      - name: Install package doc generator dependencies
+        run: pip install -r docs/requirements.txt
+
+      - name: Generate package pages from YAML
+        run: python docs/packages/generate_packages_doc.py
+
+      - name: Build with Jekyll
+        uses: actions/jekyll-build-pages@v1
+        with:
+          source: ./docs
+          destination: ./_site
+
+      - name: Deploy to GitHub Pages
+        uses: peaceiris/actions-gh-pages@v4
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./_site
+          keep_files: true