Merge multiple contexts

[]

-

{
  "@context": [
    { "@vocab": "http://example.com/vocab#" },
    { "ex": "http://example.com/ex#" }
  ],
  "foo": 3,
  "ex:bar": 5
}

{
  "http://example.com/vocab#foo": 3,
  "http://example.com/ex#bar": 5
}