Create Custom Components documentation section on DocsSite

[blackfalcon]

See issue - AlaskaAirlines/AuroDocsSite#176

Problem

See this Discussion - #526

Interestingly, the author of this Discussion put a lot of time and effort into proposing a tech update that we already support. What's learned from that is we DID NOT do a good job of describing this capability.

Currently, as stated in the Doc Site issue, we have, what I feel, is a confusing demonstration at the foot of most component landing pages. See https://auro.alaskaair.com/components/auro/button for example.

Recommendation

As proposed in the issue, the goal is to have a single landing page in the doc site that describes this capability with quality examples.

Not only should we demonstrate the ability to extend and register with an alternate name and reasons why for doing this, but we need examples on how we can extend that base element and add/edit functionality and/or UI (CSS).

The Discussion

I'd love to use thie Discussion for gathering ideas for how we can best document and illustrate the described capability to best inform our users.