Update wrcc_load() and fw13_load to load multiple stations

[EliGrosman]

One thing I realized while working on the Oregon wildfires article is that it is extremely practical to work with data from multiple raws stations.

I would like to create functionality to load data from multiple stations at once and store all of the data in a list of raws_timeseries objects. Perhaps something like:

stations <- c('station1ID' , 'station2ID', 'station3ID')

allStationData <- wrcc_load(stations, year = 2020)