PR examine tmd vs cd us totals

[donboyd5]

This PR does not change any python code.

This PR modifies the R project prepare to create and save the file cd_tmd_irs_compare.csv (in the cds/intermediate folder). This file has, for a set of tmd variables that have been mapped to published IRS Congressional District variables:

• counts and weighted values as published by the IRS for 2021, by AGI range, for the U.S. as a whole calculated from CD data (however it does not have values for individual CDs) (target)
• counts and weighted values calculated from the tmd file for 2021, by AGI range, for the U.S. as a whole (wtdvalue)
• diff: wtdvalue - target
• pdiff: diff / target

The purpose of this file is to make it easy to see which published CD values do not correspond well to the tmd data.

At present, the code does not produce any formal tables. It simply constructs and saves the comparison data, and a chunk in the file cd_compare_us_totals_tmd_vs_irs_published.qmd allows interactive examination of the comparison file. Eventually, this section of the R project will be expanded to include more variables and will present formal tables.