Add/store 'metrics reference' table in package

[alyssaobester]

It'd be nice if the package stored the table that has the longer description of the metric names somewhere. While using the results from the package, I've found that I have to keep joining those metric names to the outputs afterward in order to make tables that are readable (DS_Tim might not be super useful in a table, but the text that describes it was dry season timing is useful).