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The new registry package describes the data that must be exposed
consistently by all User Agents. For a specific piece of hardware, such
as an Oculus Touch controller, all User Agents must report the same
ordering of strings in XRInputSource.profiles. All User Agents must also
consistently map physical hardware components, such as thumbsticks, into
identical indexes within the Gamepad.buttons and Gamepad.axes arrays.
The schemas and JSON profile descriptions can be extended in the future
to unify additional XRInputSource behaviors and values.

The new assets package contains 3D asset files and JSON files with the
information necessary to animate the 3D assets in response to backing
hardware's state changes. The JSON files conform to a schema which
enumerates the relevant node names within the asset and describes visual
responses that should be applied to the 3D asset as Gamepad.buttons and
Gamepad.axes values change. The build step of the assets package merges
its profile JSON files with the matching profile JSON files in the
registry. These merged JSON files and assets can then be used directly
in the javascript library published by the motion-controllers package,
or by developers using their own asset loading and animation library.

The motion-controllers library remains 3D engine agnostic, but has been
signifcantly simplified to directly ingest the merged profile JSON files
published by the assets repository. Small changes were also made to the
viewer packages to adjust accordingly.