Small nit: perhaps it would make more sense to make this a dictionary instead, so that we can add version numbers for when a featureset was introduced?

@queengooborg I'm open to discussing the use case behind making this a dictionary, but I would prefer to start with this basic approach, to avoid scope creep.

I think that using a dictionary instead of an array of strings would have the following benefits:

• Easier to migrate codebase
  • Consumers would only have to change a small bit of code: from if (browser.accepts_flags) to if (browser.accepts.flags) (instead of browser.accepts.includes('flags'))
• Opens the possibility for adding version numbers (mentioned above)
  • This is something that I have been thinking about implementing in the future. The motivation for this is to enforce version number consistency for specific categories for when a feature category was introduced, and I've been thinking about extending it to other categories like webassembly
  • This would also mean that we don't have to release a new major version if we convert the schema to this structure
• Allows for retaining TypeScript documentation
  • If we continue to use a dictionary, we can add TypeScript/schema comments that describe what the property means in better detail

I think that using a dictionary instead of an array of strings would have the following benefits:

Done in a7ede72.