Fix presentation examples with example values.

Author: msporny

index.html

@@ -2680,7 +2680,10 @@ <h4>Presentations Including Holder Claims</h4>
   "type": ["VerifiablePresentation", "ExamplePresentation"],
   "holder": "did:example:12345678",
   "verifiableCredential": [{
-    "@context": "https://www.w3.org/ns/credentials/v2",
+    "@context": [
+      "https://www.w3.org/ns/credentials/v2",
+      "https://www.w3.org/ns/credentials/examples/v2"
+    ],
     "type": ["VerifiableCredential", "ExampleFoodPreferenceCredential"],
     "issuer": "did:example:12345678",
     "credentialSubject": {
@@ -2708,7 +2711,10 @@ <h4>Presentations Including Holder Claims</h4>
   <span class="highlight">"id": "urn:uuid:313801ba-24b7-11ee-be02-ff560265cf9b"</span>,
   "holder": "did:example:12345678",
   "verifiableCredential": [{
-    "@context": "https://www.w3.org/ns/credentials/v2",
+    "@context": [
+      "https://www.w3.org/ns/credentials/v2",
+      "https://www.w3.org/ns/credentials/examples/v2"
+    ],
     "type": ["VerifiableCredential", "ExampleAssertCredential"],
     "issuer": "did:example:12345678",
     "credentialSubject": {