Initial MWE sketch of registry app

[ml-evs]

As discussed with @PeterKraus and @unkcpz in today's office hours.

<create fresh env>
pip install -r requirements.txt
python app.py &
curl localhost:5000/filetypes

This just covers the "registered file types/extractors -> web API pipeline". Many things missing:

• [x] The actual schema to use (probably to be developed in https://github.com/marda-alliance/metadata_extractors_schema? -- or separate schema for registry)
• [ ] Mechanism in CI/server for taking extractor definition and trying to run it on example data that matches the input format
• [ ] Rendering a nice UI
• [ ] Storage in a more persistent database (might not even be needed for a long time -- currently just using a in-memory fake MongoDB that can be deployed serverless and will do very slow free-text search over our small number of entries)