docker: add git revision to version during docker build

Using a "local version identifier" per PEP 440,
the version looks like: 1.3.0+d7abeb3

PEP for reference: https://peps.python.org/pep-0440/

This will help distinguish ETL builds from each other while we still
build directly from git.

Dockerfile

@@ -38,6 +38,7 @@ RUN pip3 install nltk
 RUN python3 -m nltk.downloader -d /usr/local/share/nltk_data averaged_perceptron_tagger
 
 COPY . /app
+RUN sed -i "s/\(__version__.*\)\"/\1+`git -C /app rev-parse --short HEAD`\"/" /app/cumulus_etl/__init__.py
 RUN --mount=type=cache,target=/root/.cache \
   pip3 install /app
 RUN rm -r /app