windows fix path

Author: cvanelteren

.github/workflows/build.yml

@@ -87,7 +87,7 @@ jobs:
           CIBW_BEFORE_ALL: ${{ matrix.before_all }}
           CIBW_TEST_REQUIRES: pytest
           CIBW_TEST_COMMAND: "cd {project}/packages/basemap && pytest"
-          CIBW_TEST_COMMAND_WINDOWS: "dir {project}/packages/basemap && pytest"
+          CIBW_TEST_COMMAND_WINDOWS: "dir {project}\\packages\\basemap && pytest"
           CIBW_ENVIRONMENT: >-
             GEOS_VERSION="3.6.5"
             GEOS_DIR="$(pwd)/extern"