Add an initial GitHub Action declaration

Dockerfile

@@ -0,0 +1,18 @@
+FROM python:3.7-slim
+
+LABEL "maintainer"="Sviatoslav Sydorenko <wk+re-actors@sydorenko.org.ua>"
+LABEL "repository"="https://github.com/re-actors/pypi-action"
+LABEL "homepage"="https://github.com/re-actors/pypi-action"
+
+LABEL "com.github.actions.name"="pypi-action"
+LABEL "com.github.actions.description"="Upload Python distribution packages to PyPI"
+LABEL "com.github.actions.icon"="upload-cloud"
+LABEL "com.github.actions.color"="yellow"
+
+ENV PYTHONDONTWRITEBYTECODE 1
+ENV PYTHONUNBUFFERED 1
+
+RUN pip install --upgrade --no-cache-dir twine
+
+ENTRYPOINT ["twine"]
+CMD ["upload", "dist/*"]