[CSS Modules] Use Import Map Syntactic Sugar (#1156)

Updates to the spec to use the Import Map Syntactic Sugar as proposed in w3ctag/design-reviews#1000 (comment)

- Updates to Module Map Key section was moved to "Alternate Proposals"
- A new section "Syntactic Sugar For Import Maps with DataURI" was added
- Existing "Detailed Parsing Workflow" was updated with new approach
- Other sections were updated as necessary with the new model
- All existing Open Issues closed with new approach (🎉), but a new Open Issue was added for the "duplicate specifier but different type" behavior this breaks.
- "Javascript" was converted to "JavaScript" everywhere for consistency

Author: KurtCattiSchmidt