Add DC income tax COLA

In #4306 @shuyu7zhan is adding uprating based on the IRS factor. However, DC's differs from this; instead of the June-June change, it's calendar year based:

>(12) The term "cost-of-living adjustment" means, for any calendar year, the difference between the Consumer Price Index for the preceding calendar year and the Consumer Price Index for the base year, divided by the Consumer Price Index for the base year.

https://code.dccouncil.gov/us/dc/council/code/titles/47/chapters/18/subchapters/VI

This is low priority as it's going to be pretty close.