added workflow to publish to pip

.github/workflows/publish_pypi.yml

@@ -0,0 +1,38 @@
+name: Publish Icesat2 to PyPI
+
+on:
+    pull_request: {}
+    push:
+        branches:
+          - feature-publish-pypi
+#  release:
+#    types: [published]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v2
+
+    - name: Set up Python
+      uses: actions/setup-python@v2
+      with:
+        python-version: 3.8
+
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install build twine
+
+    - name: Build package
+      run: |
+        python -m build
+
+    - name: Publish to PyPI
+      env:
+        TWINE_USERNAME: "__token__"
+        TWINE_PASSWORD: ${{ secrets.PYPI_TOKEN }}
+      run: |
+        python -m twine upload --skip-existing --repository pypi dist/*