Add API docs for disco

[s314cy]

Description

Provides discojs (discojs-{core,node,web}) with centralized docs, under the form of HTML pages accessible at some path from epfml.github.io/disco. To do so, we use the typedoc pkg which generates HTML API docs based on code documentation.

Additions & Changes

• add and config the typedoc pkg
• add code documentation
• ensure the docs tree provides the right tree structure (done either by adding typedoc configs or by slightly modifying the discojs exports tree)
• expose the HTML docs on a path from epfml.github.io/disco

[s314cy]

While the HTML docs can be built using npm run docs within any Disco subproject (core, web, node), exposure to the web is not a priority and thus is left for a future PR.