Linter shows incorrect warning for external context references

[RinkeHoekstra]

It is fine in JSON-LD to refer to an external context, either by explicit URI, or by a relative one.

However, the linter currently raises the warning Value for the JSON-LD syntax token "@context" of "someexternalcontext.jsonld" is invalid if the value for the @context is anything other than an object or an array of objects.

See https://www.w3.org/TR/json-ld11/#example-5-referencing-a-json-ld-context