Update docs and add example app

[kubkon]

This commit updates docs to reflect the existence of the new CRA template for FluentUI that uses react-scripts for dev/build paths. It also adds an example FluentUI app that the user can examine while following along the 'Getting Started' section of the docs.

[kubkon]

cc @JasonGore

[kubkon]

Thanks for the PR! I have some questions I'd like to work out with you

Thanks for the review, and absolutely, please keep the review comments coming!

[kubkon]

Comments addressed @JasonGore, ready for the next round of reviews!

[JasonGore]

Please consider not rebasing / force pushing every time you update this branch. It makes pulling updates painful. Commits are squashed anyways, so doing rebases / force pushes doesn't really add any benefit.