Avoid using "anchors" block for referencing other specs in Bikeshed #1763
Description
Per the discussion in #1762 (comment).
The current use of the "anchors" block in the Bikeshed file to reference definitions from other specifications (e.g., HTML, Fetch, Storage) is problematic. So,
- Update references to W3C Specs from the "anchors" block with explicitly export definitions.
- Use link-defaults for common definitions.