Add workflow to build the site with Jekyll and deploy using ltd-upload

.github/workflows/docs.yaml

@@ -0,0 +1,67 @@
+name: Python CI
+
+env:
+  # Default Python version used for all jobs other than test, which uses a
+  # matrix of supported versions. Quote the version to avoid interpretation as
+  # a floating point number.
+  PYTHON_VERSION: "3.12"
+
+"on":
+  merge_group: {}
+  pull_request: {}
+  push:
+    branches-ignore:
+      # These should always correspond to pull requests, so ignore them for
+      # the push trigger and let them be triggered by the pull_request
+      # trigger, avoiding running the workflow twice.  This is a minor
+      # optimization so there's no need to ensure this is comprehensive.
+      - "dependabot/**"
+      - "gh-readonly-queue/**"
+      - "renovate/**"
+      - "tickets/**"
+      - "u/**"
+  release:
+    types: [published]
+
+jobs:
+
+  docs:
+
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0 # full history for setuptools_scm
+
+      - name: Install Ruby and other prerequisites
+        run: sudo apt-get install ruby-full build-essential zlib1g-dev
+
+      - name: Install Jekyll
+        run: gem install bundler jekyll
+
+      - name: Setup Ruby Gems environment
+        run: |
+          echo 'export GEM_HOME="$HOME/gems"' >> ~/.bashrc
+          echo 'export PATH="$HOME/gems/bin:$PATH"' >> ~/.bashrc
+          source ~/.bashrc
+
+      - name: Build the schema browser site
+        run: jekyll build
+
+      # Only attempt documentation uploads for tagged releases and pull
+      # requests from ticket branches in the same repository.  This avoids
+      # version clutter in the docs and failures when a PR doesn't have access
+      # to secrets.
+      - name: Upload to LSST the Docs
+        uses: lsst-sqre/ltd-upload@v1
+        with:
+          project: "sdm-schemas"
+          dir: "_site"
+          username: ${{ secrets.LTD_USERNAME }}
+          password: ${{ secrets.LTD_PASSWORD }}
+        if: >
+          github.event_name != 'merge_group'
+          && (github.event_name != 'pull_request'
+              || startsWith(github.head_ref, 'tickets/'))