Update pages/ActivityContent/Associated/Attachments.md

Link to specification of MIME type per Shannon's suggestion

Co-authored-by: Shannon Wells <[email protected]>

Author: wesbiggs

pages/ActivityContent/Associated/Attachments.md

@@ -222,7 +222,7 @@ The link must contain a relationship identifier in the form of a DSNP Attribute
 | `type` | [Activity Vocabulary 2.0](https://www.w3.org/TR/activitystreams-vocabulary/#dfn-type) | YES | Identifies the type of the object | MUST be set to `Link` |
 | `rel` | [Activity Vocabulary 2.0](https://www.w3.org/TR/activitystreams-vocabulary/#dfn-id) | YES | The attestation's attribute set type | MUST be a DSNP [Attribute Set Type](../../DSNP/AttributeSets.md#attribute-set-type) corresponding to the referenced credential document |
 | `href` | [Activity Vocabulary 2.0](https://www.w3.org/TR/activitystreams-vocabulary/#dfn-href) | YES | The URL for the associated Verifiable Credential | MUST be a [Supported URL Schema](../Overview.md#supported-url-schema) |
-| `mediaType` | [Activity Vocabulary 2.0](https://www.w3.org/TR/activitystreams-vocabulary/#dfn-mediatype) | YES | MIME type of `href` content | MUST be set to `application/vc+ld+json` |
+| `mediaType` | [Activity Vocabulary 2.0](https://www.w3.org/TR/activitystreams-vocabulary/#dfn-mediatype) | YES | MIME type of `href` content | MUST be set to [`application/vc+ld+json`](https://w3c.github.io/vc-data-model/#vc-ld-media-type) |
 | `hash` | [DSNP 1.0](Hash.md) | YES | Array of hashes for linked content validation | MUST include at least one [supported hash](Hash.md#supported-algorithms) |
 
 ### Attestation