Add Solar Alabama dataset

[WenjieDu]

1. Dataset description

It contains the solar power production records in the year 2006,
which are sampled every 10 minutes from 137 PV plants in Alabama State.

2. Check open-source status

• The dataset implementation is publicly available

3. Provide useful information for the implementation

https://www.nrel.gov/grid/solar-power-data.html

https://github.com/laiguokun/multivariate-time-series-data