ContextKt

Defines the notion of a *Render Context* for server-side pages in Gust. This protocol message is filled out with data
as configured by the developer (from `application.yml` and the active controller, as applicable) and provided as an
injected value to all server-side render operations.

When preparing context in Gust, adding a static script or stylesheet is done through `Context`. Setting page metadata
like the title, keywords, and manifest - also all done through `Context`. This of course has the added benefit of
being completely serializable, repeatable, and so on (i.e. all the benefits Protobuf brings).

Major context modules include:
- *Metadata*: Page-level metadata.
- *OpenGraph*: Properties for OG tags.
- *Twitter*: Properties for Twitter cards.
- *AppManifest*: Information to link or derive a web application manifest.
- *Styles*: Stylesheets and inline head-injected styles ("lifted styles").
- *Scripts*: Scripts to include, and inline head-injected logic ("lifted JS").