In order to use the JS API directly, and enable use cases like T137148, we should convert the hard dependency with "mediawiki.router" into a soft dependency.

In other words:

• the code should not require the router when creating a map
• the code should be able to open a map full screen without the router
• the code should be able to close a full screen map without the router.

As a developer, I should have a simple parameter or option, when I create a map, to decide whether I want to leverage the router or not.