Feature request: Make `getQueryVariable` iframe aware or at least allow to pass launch parameters to `launch` explicitly

[ralokt]

The current implementation of ADL.launch uses getQueryVariable [1], which assumes that it will always be able to get the launch parameters from window.location. This is not true if window is an iframe, for example for an embedded H5P on a Moodle page.

It would be great if this use case could be supported somehow, perhaps by trying to get launch parameters from the parent iframe (if it exists) as a fallback, or by allowing to override the launch parameters by passing them explicitly.

[1] https://github.com/adlnet/xAPIWrapper/blob/d6637d3e2a63f728d467b97ba111e85410de639c/src/xapi-launch.js#L3