Republishing CSS Motion Path

The motion path spec has received lots of changes since
the FPWD, especially after merging some properties
from CSS Round Display.

  - Renamed motion-path to offset-path, with added support for ray() paths.
  - Renamed motion-offset to offset-distance.
  - Renamed motion-rotation to offset-rotate.
  - Added offset-position to specify the initial position of the path.
  - Added offset-anchor to specify the origin point of the element.

The resolutions from Tokyo have been incorporated,
and most of the issues identified in the TAG review
have been resolved.

Interaction with the 'position' property has been clarified,
as has the meaning of 'contain'.

We think the draft is ready for republication.
https://drafts.fxtf.org/motion-1/

Eric and Jihye.