(feature, typescript): Use generator-cli to generate reference.md

[amckinney]

Feature

This updates the TypeScript generator to always generate the reference.md (this was previously feature flagged). An example of the generated markdown is shown below:

Improvements

Additionally, the generator now uses the generator-cli to generate the reference.md file, and this change fixes a bug where we were generating multiple sections for a single endpoint (one section for each example). We now only generate a single section per endpoint, preferring the first configured example over the rest.

This also refactors the generator-cli client abstraction so that it simply acts as a way to call the CLI methods - a new ReadmeGenerator abstraction is introduced to encapsulate all of the logic required to create the ReadmeConfiguration (which acts just like the ReferenceGenerator).