MIMIC-III is missing Charlson Comorbidity Index

MIMIC-III only seems to have Elixhauser, which is pretty much the same as Charlson. We have [this query for MIMIC-IV](https://github.com/MIT-LCP/mimic-code/blob/81deb222071cd25f861fdb817fec3adda3c43c21/mimic-iv/concepts/comorbidity/charlson.sql), shall we try to replicate it in MIMIC-III?