add hooks link

Author: brettmarquard

docs/specification/1.0.md

@@ -107,7 +107,7 @@ An EHR calls a CDS Service by `POST`ing a JSON document to the service as descri
 
 Field | Optionality | Type | Description
 ----- | ----- | ----- | --------
-`hook` | REQUIRED | *string* | The hook that triggered this CDS Service call<br />(todo: link to hook documentation)
+`hook` | REQUIRED | *string* | The hook that triggered this CDS Service call. See [Hooks](../hooks/index.md).
 <nobr>`hookInstance`</nobr> | REQUIRED | *string* | A UUID for this particular hook call (see more information below)
 `fhirServer` | OPTIONAL | *URL* | The base URL EHR's [FHIR](https://www.hl7.org/fhir/) server. If fhirAuthorization is provided, this field is REQUIRED.  The scheme should be `https`
 `fhirAuthorization` | OPTIONAL | *object* | A structure holding an [OAuth 2.0][OAuth 2.0] bearer access token granting the CDS Service access to FHIR resources, along with supplemental information relating to the token. See the [FHIR Resource Access](#fhir-resource-access) section for more information.