Adding support for nightly builds

.github/workflows/nightly.yml

+name: Nightly
+on:
+  schedule:
+    - cron: "0 0 * * *"
+
+jobs:
+  build_and_publish:
+    name: Build source distribution
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+      - uses: actions/setup-python@v2
+        with:
+          python-version: "3.9"
+      - name: Install dependencies
+        run: |
+          python -m pip install -U pip
+          python -m pip install build
+      - name: Build the sdist
+        run: python -m build --sdist .
+        env:
+          BUILD_AESARA_NIGHTLY: true
+      - uses: pypa/gh-action-pypi-publish@v1.4.2
+        with:
+          user: __token__
+          password: ${{ secrets.nightly_pypi_secret }}

setup.py

 #!/usr/bin/env python
+import os
 import sys
 
 from setuptools import find_packages, setup
@@ -59,6 +60,24 @@ install_requires = [
 if sys.version_info[0:2] < (3, 7):
     install_requires += ["dataclasses"]
 
+# Handle builds of nightly release
+if "BUILD_AESARA_NIGHTLY" in os.environ:
+    nightly = True
+    NAME += "-nightly"
+
+    from versioneer import get_versions as original_get_versions
+
+    def get_versions():
+        from datetime import datetime, timezone
+
+        suffix = datetime.now(timezone.utc).strftime(r".dev%Y%m%d")
+        versions = original_get_versions()
+        versions["version"] = versions["version"].split("+")[0] + suffix
+        return versions
+
+    versioneer.get_versions = get_versions
+
+
 if __name__ == "__main__":
     setup(
         name=NAME,
@@ -66,6 +85,7 @@ if __name__ == "__main__":
         cmdclass=versioneer.get_cmdclass(),
         description=DESCRIPTION,
         long_description=LONG_DESCRIPTION,
+        long_description_content_type="text/x-rst",
         classifiers=CLASSIFIERS,
         author=AUTHOR,
         author_email=AUTHOR_EMAIL,