Revert "Add GitHub Actions config"

This reverts commit b847c85b

.github/workflows/build.yml

-name: Building and testing
-on: [push]
-jobs:
-  building:
-    runs-on: ubuntu-latest
-    container:
-      image: alexpovel/latex
-      # Need root, otherwise this exact issue occurs:
-      # https://github.community/t/permission-problems-when-checking-out-code-as-part-of-github-action/202263
-      options: --user root
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v3
-      - name: Run preflight checks
-        run: make preflight
-      - name: Build all LaTeX PDFs
-        run: make tex
-      - name: Build README PDF
-        run: make README.pdf
-      - name: Archive compilation artifacts
-        uses: actions/upload-artifact@v3
-        with:
-          name: pdfs
-          path: ./*.pdf
-          if-no-files-found: error
-  testing:
-    needs: building
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v3
-      - uses: actions/setup-python@v3
-        with:
-          python-version: "3.10"
-      - uses: snok/install-poetry@v1
-        with:
-          virtualenvs-create: false
-      - name: Install Python dependencies
-        working-directory: ./tests  # Needs to find pyproject.toml file
-        run: poetry install
-      - name: Test the suite itself
-        run: make test-self
-      - uses: actions/download-artifact@v3
-        with:
-          name: pdfs  # Specify name, else it'll be downloaded to a subdirectory
-      - name: Test generated PDFs
-        run: make test-pdfs