Handle yarn instant search build and reduce bundle size

A small MVC for:

• #854 (closed)
• #725 (closed)

This merge is the first of 3 merges designed as ~"feature::maintenance" for the Docs site 😄

Merge	You are here
Fix build tools	🤘
Minify Client JavaScript	TBA
Handle sidebar CSS	TBA

This merge allows us to reduce the bundle size on pages using the gitlab/ui components:

Before	After

And, allows us to leverage external libs correctly in the build such as instantsearch:

Note

We still cannot import components via: import { GlLink } from '@gitlab/ui'; yet and need raw imports: import GlLink from '@gitlab/ui/dist/components/base/link/link';

This is due to the needing to handle SVG imports correctly and peer libs that gitlab/ui depends on which I have not found a solution for yet.

Closes #854 (closed) Closes #725 (closed)