test: Poetry on Windows

Conda is installed on the runner by default, but we need to do
additional setup
<actions/runner-images#3477 (comment)>
to make it available on the command line.

.github/workflows/test.yml

@@ -67,6 +67,7 @@ jobs:
         runner:
           - macos-12
           - ubuntu-22.04
+          - windows-2022
         python:
           - "3.8"
           - "3.9"
@@ -77,6 +78,8 @@ jobs:
             pip-cache-dir: ~/Library/Caches/pip
           - runner: ubuntu-22.04
             pip-cache-dir: ~/.cache/pip
+          - runner: windows-2022
+            pip-cache-dir: ~\AppData\Local\pip\Cache
     steps:
       - name: Check out repository
         uses: actions/checkout@v3.3.0
@@ -109,8 +112,18 @@ jobs:
         run: brew install gdal
         if: startsWith(runner.os, 'macOS')
 
+      - name: Setup Conda on Windows
+        uses: s-weigand/setup-conda@v1.1.1
+        with:
+          conda-channels: conda-forge
+        if: startsWith(runner.os, 'Windows')
+
+      - name: Install GDAL on Windows
+        run: conda install --channel=conda-forge --quiet --yes gdal
+        if: startsWith(runner.os, 'Windows')
+
       - name: Upgrade pip
-        run: pip install --upgrade pip
+        run: python -m pip install --upgrade pip
 
       - name: Install Poetry
         run: pip install poetry