ci: add deploy workflow (#1594)

This patch adds a deploy workflow for automatically deploying the package to PYPI when a release is "published".

According to the docs for "published":

> published: a release, pre-release, or draft of a release is published

[source](https://docs.github.com/en/developers/webhooks-and-events/webhook-events-and-payloads#release)

Unfortunately Github actions [doesn't have a manual approval step](https://github.community/t/github-actions-manual-trigger-approvals/16233/85) which would be ideal to use here.

This is based off of the [cibuildwheel example](https://github.com/joerick/cibuildwheel/blob/5c4767899dc4418b509a2d7ccfde07d33ab29e28/examples/github-deploy.yml) and our modifications made in #1554.

Co-authored-by: Brett Langdon <[email protected]>

Author: Kyle-Verhoog

.github/workflows/build_deploy.yml

@@ -0,0 +1,79 @@
+name: Build
+
+on:
+  pull_request:
+  release:
+    types:
+      - published
+
+jobs:
+  build_wheels:
+    name: Build wheels on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-18.04, windows-latest, macos-latest]
+
+    steps:
+      - uses: actions/checkout@v2
+        # Include all history and tags
+        with:
+          fetch-depth: 0
+
+      - uses: actions/setup-python@v2
+        name: Install Python
+        with:
+          python-version: '3.8'
+
+      - name: Install cibuildwheel
+        run: |
+          python -m pip install cibuildwheel==1.5.5
+
+      - name: Build wheels
+        run: |
+          python -m cibuildwheel --output-dir wheelhouse
+        env:
+          CIBW_SKIP: pp* cp27-win*
+
+      - uses: actions/upload-artifact@v2
+        with:
+          path: ./wheelhouse/*.whl
+
+  build_sdist:
+    name: Build source distribution
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        # Include all history and tags
+        with:
+          fetch-depth: 0
+
+      - uses: actions/setup-python@v2
+        name: Install Python
+        with:
+          python-version: '3.7'
+
+      - name: Build sdist
+        run: |
+          pip install cython
+          python setup.py sdist
+
+      - uses: actions/upload-artifact@v2
+        with:
+          path: dist/*.tar.gz
+
+  upload_pypi:
+    needs: [build_wheels, build_sdist]
+    runs-on: ubuntu-latest
+    if: github.event_name == 'release' && github.event.action == 'published'
+    steps:
+      - uses: actions/download-artifact@v2
+        with:
+          name: artifact
+          path: dist
+
+      - uses: pypa/gh-action-pypi-publish@master
+        with:
+          user: __token__
+          password: ${{ secrets.PYPI_TOKEN }}
+          # To test: repository_url: https://test.pypi.org/legacy/