Need to create pyhealth[nlp] pyhealth[graph] dependencies in the .toml file

[jhnwu3]

There are going to be an increasingly large number of approaches that have weird custom extra dependencies. It would be worthwhile to enable the downloading of other foundational dependencies in PyHealth. However, not every user wants to download these packages necessarily.

• pyhealth[nlp]
  spacy, scispacy, etc. (some version)

• pyhealth[graph]
  pygeometric (some version number)