Add ingest workflow

[victorlin]

Add an ingest workflow to the repository based on pathogen-repo-guide and tutorial in docs.

Potential data sources:

1. NCBI GenBank – I will start with this
2. Pathoplexus
3. artic-network/ebolavirus – a curated subset of accessions from (1)?
4. Fauna – was used for https://nextstrain.org/ebola, but not high priority.

At the very least this will need a lot of work to label division, which doesn't seem to be listed often on GenBank (see OR084909 or KU296360)

[huddlej]

It would be really cool if a Pathoplexus-based workflow could serve as the starting point for a docs.nextstrain.org tutorial on how to create a Nextstrain build with Pathoplexus.

[jameshadfield]

2018-20 DRC ZEBOV data is in the INRB's GitHub

[victorlin]

I briefly explored ingest from Pathoplexus. Summarized as an unmerged commit: 99ec7ad

While it mostly works, I'll stick with GenBank for now. My main motivation was to see if the Pathoplexus endpoint came with more metadata compared to NCBI datasets ingest, but I think it's about the same.