Add `emanote query`

[srid]

https://github.com/srid/emanote/discussions/178

To begin with, add emanote query --export which basically dumps the export.json file to stdout.

Later on, we can implement some of https://neuron.zettel.page/query as needed.

Two uses of this command:

• In editors like vim, one can invoke it without being dependent on the live server already running (even though it would be slower to shell out to emanote)
• Act as a demonstration of using Emanote as a library to get the full Model of one's notebook.