Batch add

[beckyjackson]

Right now, add only accepts one file path, but it would be really beneficial to add all TSV files within a directory (e.g. add templates/*.tsv). The downside is that any --description would be applied to all (as well as frozen rows and columns), but maybe that's not a problem?

[jamesaoverton]

This would be convenient, but doesn't seem urgent to me.

One note: with most of the projects that I care about, I want the sheets added in a certain order, not just the alphabetical order from a glob *.