Update CI to install GDAL

Author: sgreenbury

.github/workflows/ci.yml

@@ -42,6 +42,22 @@ jobs:
           python-version: ${{ matrix.python-version }}
           allow-prereleases: true
 
+      - name: Setup Miniconda
+        uses: conda-incubator/setup-miniconda@v3.0.4
+        with:
+          auto-update-conda: true
+          python-version: ${{ matrix.python-version }}
+          channels: conda-forge
+          channel-priority: strict
+          auto-activate-base: false
+          miniforge-version: latest
+          use-mamba: true
+
+      - name: Install GDAL
+        run: |
+            mamba install conda-forge::gdal
+            python -m pip install .[test]
+
       - name: Install package
         run: python -m pip install .[test]