Plugin framework for documentation

Suggestion: Implement a plugin framework allowing to easily extend `documentation`

I have two distinct use cases for this:
* Being able to add a parser (for example C++) and to hook it in `buildInternal` along `parseJavaScript` and also in `isJSDocComment`
* Being able to support custom jsdoc tags - by plugging in the parser itself by tag name - as I have a very specific need, namely having a very large number of synchronous and asynchronous functions with the same parameters (+ callback for the async versions) that I need to be ideally able to document with a single block as to avoid any errors and render future maintenance easier

I am willing to work on an implementation if we can settle on a (somewhat) stable API