Failure to validate when keys are JSON-LD keywords

[kelvinqian00]

Issue: When validating keys that are JSON-LD keywords such as @id and @type (rather than the aliased variants id and type that do not have the @ symbol), the library fails to recognize the keys and declares them missing.

Reproduction: Run validate-profile on the cmi5 profile, which uses @id and @type rather than id and type.

Does this need to be fixed? Maybe, but also maybe not. After all, although @id and @type are legal keywords in JSON-LD, the xAPI Profile spec defines these properties assuming they are the aliased versions. So the context namespace should have these cases in mind, but the rest of the library do not need to.