feat: add dags ci github action

[bibliotechy]

Add github workflows for doing basic checking of dags and then deploying them to s3.

Creates a basic dags directory so the tests have something to check

[amywieliczka]

I'm a bit confused by the re-ordering of import statements. At first it looked like you were grouping built-in modules vs. 3rd-party modules, vs. our own modules, grouping each group by "import " vs. "from ", and then ordering each group alphabetically by module name. But I don't think metadata_mapper/mappers/mapper.py (some of our own modules are grouped with 3rd party modules) or metadata_mapper/mappers/oai/oai_mapper.py (alphabetical sorting with ., and ..mapper) quite follow this sort order. Not a huge deal, but I do want to make sure I understand any order you're asserting here so I can try to maintain it as I move forward.

Also, I've not used a Pipfile or pipenv before. I'm confused by the relationship between dags/Pipfile and dags/requirements.txt. Since we had previously conceived of running these tasks in separate aws lambdas, there's a bit of a proliferation of requirements.txts in this repo. I'm not quite sure if I still see the value in having all of these separate requirements.txts anymore though.

Finally, it seems that universally throughout the codebase, instances of from . import settings need to be replaced with from .. import settings

[amywieliczka]

Thanks!