adds install in github workflow

.github/workflows/nngeometry.yml

@@ -20,6 +20,7 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           pip install flake8 pytest
+          pip install .
           if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
       - name: Lint with flake8
         run: |