Mappings for Interop 2026 focus areas to web-features

[captainbrosset]

This isn't quite ready to be reviewed. I'll update this when it is.

TODO:

• Wait for Add WebAssembly JavaScript Promise Integration (JSPI) feature web-platform-dx/web-features#3791
• Wait for Add Navigation API precommit handler feature web-platform-dx/web-features#3792
• Wait for Extract formData out of Fetch and into a new feature web-platform-dx/web-features#3813
• Figure out if we're able to create new web-features for interop-2026-fetch
  • The PR above takes care of the formData part of this focus area.
  • I don't think we need other features. The remaining parts of this focus area are mime-type support and Range header support. Both of these are tracked in BCD in parts that aren't necessarily related to the Fetch API.
• Figure out whether "Timing of scroll events relative to animation events" can/should be represented as a web-feature.
  • I don't think we need a web-features entry for this. I consider this as a bug.