Added tests for `@json` field testcase in framing

[pasquale95]

As suggested in the issue #142, I've added a test collection to better define what is expected when framing over a @json field.

[w3cbot]

gkellogg marked as non substantive for IPR from ash-nazg.

[gkellogg]

I updated your branch with the manifest entries required. Without the suggested update, the result will be in the expanded form:

{
  "@context": {
    "ex": "http://example.org/vocab#"
  },
  "@id": "http://example.org/test/#library",
  "@type": "ex:Library",
  "ex:info": {
    "@value": {
      "author": "JOHN",
      "pages": 200
    },
    "@type": "@json"
  }
}

But, it fails with the update, which will require some investigation.

[gkellogg]

I've updated this to be a passing test.