Suggested Lexicon: `site.standard.code.sandbox|pen` #6

Another standard want for many sites is a code sandbox, or code pen.

code.sample is a non-interactive sample of code for any single language.

code.sandbox would be an interactive sample of code for any group of languages.

A canonically simple case would be creating a code pen of our own, with:

HTML
CSS
JavaScript
An Optional Import Map (JSON)

A less canonical example might consist of:

An arbitrary language
A sandbox service URL

In order to encompass both scenarios, I suggest the following lexicon:

site.standard.code.sandbox#

A code sandbox. Code sandboxes can contain multiple languages and should be able to run interactively where possible.

Property	Type	Description
`$type`	`[string]`	The type of the object. Must be `site.standard.code.sandbox`.
`title`	`[string]`	The title of the sandbox
`sandbox`	`[object]`	An object containing code to run in the sandbox. Should contain html, css, javascript, and/or an import map.
`sandboxUrl`	`[uri]`	A url for a sandbox service, or a url to the sandbox. If `sandbox` is empty, this should be treated as an external link
`createdAt`	`[datetime]`	The time the sandbox was created

In case anyone is wondering, I'm suggesting sandbox be optional so that a sandboxUrl can just point to an existing sandbox (thus enabling people to easily link existing sandboxes like codepen)