precip station layers

[ksonda]

I've been part of separate convos w/ @jkreft-usgs and @amabdallah about getting precip-type sites in either NLDI or here. Notably

-SNOTEL -NADP

Any others?

What about straight rain stuff like

• Everything in NCEI
• CoCoRaHS (most of these will be in GHCN within NCEI but ones with <100 validated observations wont be yet)
• [State Climate Offices] https://stateclimate.org/state_programs/

Can we have /ref/precip-sites or something similar to /ref/gages ? Should Snowpack monitoring be a different thing?