feat: proof-of-concept API doc generation for jspm.org

[Bubblyworld]

See #23. Adds a script that generates API documentation for @jspm/generator using
typedoc and spits in out into the public_html/api/generator directory. We can
change it easily to support versioning and the rest of the @jspm packages,
but we'll have to wire each package we want to support with a tsconfig.json
and a typedoc.json file.

At the moment I haven't added any links to the new docs, but you can see them
by going to the /api/generator path.

[Bubblyworld]

The default theme:

[Bubblyworld]

Screenshot showing dark mode and version box.