.github/workflows: Install soundfile and libsndfile.

"build": pip install will install the Python soundfile package.  On
Windows/MacOS, this will install a binary wheel package that includes
a private copy of libsndfile; on Ubuntu, it will install a generic
package that requires us to install libsndfile separately.

"test-deb10-i386": python3-soundfile installs the Python soundfile
package and also depends on libsndfile1.

Author: Benjamin Moody

.github/workflows/run-tests.yml

@@ -28,6 +28,10 @@ jobs:
         run: |
           python -m pip install --upgrade pip poetry
           pip install ".[dev]"
+      - name: Install libsndfile
+        if: startsWith(matrix.os, 'ubuntu')
+        run: |
+          sudo apt-get install -y libsndfile1
       - name: Run tests
         run: pytest
       - name: Validate poetry file
@@ -48,6 +52,7 @@ jobs:
                   python3-pandas \
                   python3-requests \
                   python3-scipy \
+                  python3-soundfile \
                   python3-pytest \
                   git