Extract tutorial issues

[mmcdermott]

1. Should update the description fo dod and link to the part of the documentation on it: https://mimic.mit.edu/docs/iv/modules/hosp/patients/#dod

[mmcdermott]

given if should be given it

[mmcdermott]

Need to be a bit more conceptual and remind of some of the principles of MEDS a bit more (e.g., null time events, rows being complete observations, static vs. dynamic vs. time-derived.)

should have a section before digging into the data about the "format" of a MEDS measurement (e.g., what we're building up to)

[mmcdermott]

Need to add some learning call-outs (ideally both about data and extraction)

[mmcdermott]

first note on complexity out of order with the specification

[mmcdermott]

built up tutorial is a bit out of sync with current MIMIC ETL which has language and race and marital status extra columns not measurements.