feat(routing): add TestRoutingContext

[UberMouse]

Exposes a public interface to rendering the routing context outside of an xstate-tree root, for tests/storybook etc

[github-actions[bot]]

:tada: This PR is included in version 4.1.0-beta.6 :tada:

The release is available on:

• npm package (@beta dist-tag)
• GitHub release

Your semantic-release bot :package::rocket:

[github-actions[bot]]

:tada: This PR is included in version 4.1.0 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: