Support for non-Cornell Dining eateries

[willbarkoff]

Right now, the Cornell Dining API only returns information for Cornell Dining-run eateries. Others exist, some popular examples being Terrace, Temple of Zeus, and Manndible. Some of these accept BRBs, while others don't.

Eatery hardcodes these, and a similar approach would likely be ideal – potentially Foodie could offload this onto the Eatery API (it's a pretty simple GraphQL API, eatery-backend.cornellappdev.com), though that feels wrong. Potentially Foodie could just support the same format that eatery-backend does for external eateries and the JSON files could be kept in sync?

https://github.com/cuappdev/eatery-backend/blob/master/static_sources/externalEateries.json