Add exports

[batson]

Hello!

I believe you shared with me some code for exporting a baltic tree as a Nextstrain JSON. I expect it would be widely useful at this point.

exportJSON perhaps?

[evogytis]

Hey, Josh!

I've gotten clade padding working and will implement a rudimentary export to JSON soon and push everything to pip. For now feel free to use this workaround: #20

Best,
G.

[evogytis]

Hey Josh,

I've decided that exporting to auspice JSON is better done via a separate notebook rather than integrated into baltic itself because the automation of transfering all the traits from baltic into JSON might require more work than I can dedicate right now, as well as the meta portion of the JSON requiring a lot of customisation.
Here's the notebook I prepared for the baltic gallery (it's not yet up on the website though): https://github.com/phylo-baltic/baltic-gallery/blob/gh-pages/assets/notebooks/advanced-auspice-export.ipynb
Let me know if that addresses your need or if you run into any problems!

Best,
G.