PR include raw data in repo

[donboyd5]

This PR does not modify any python code.

This PR includes raw data files needed for state targeting. While we will only target 2021, it includes files for each year from 2015 (the year of the PUF) through 2021, which can allow useful side analyses. The PR includes 3 files per year from SOI Historical Table 2, plus one Excel workbook. Years are designated by their last 2 digits [yy].

The files are:

• [yy]in54cm.xlsx or similar, from SOI: each file has human-readable SOI values for all states for the year.
• [yy]in54cmcsv.csv or similar, from SOI: file with SOI values for all states for the year.
• [yy]incmdocguide.doc, from SOI: descriptive documentation, including a table of variables and their descriptions
• soi_states_variable_documentation.xlsx, hand-created by me from the .doc files: has a sheet for each year with its documentation table. NOT intended to be edited by users.