Add descriptive research to section on research types

[jstrothman]

The Research types section includes foundational, generative, and evaluative, but doesn't have descriptive research.

Let's add something like: Descriptive The observation and description of what you’re studying. Descriptive research is what you do when you already have a problem and need to understand the context entirely. (The above is taken from @boonerang training day 1. Will link, once it's shared)