#242: Added definition for prefetch key

Author: brynrhodes

docs/specification/1.0.md

@@ -195,7 +195,7 @@ Similarly, each EHR will decide what FHIR resources to authorize and to prefetch
 
 A _prefetch template_ is a `read` or `search` request that describes relevant data needed by the CDS Service. To allow for prefetch templates that are dependent upon the particular CDS Service request, prefetch templates may include references to context using _prefetch tokens_. A prefetch token is an identifier in a prefetch template that is replaced by a value from the hook context to construct the FHIR URL used to request the prefetch data. 
 
-The `prefetch` field of a CDS Service description defines the set of prefetch templates for that service, providing a prefetch key for each one that is used to provide the prefetch data in the CDS request.
+The `prefetch` field of a CDS Service description defines the set of prefetch templates for that service, providing a _prefetch key_ for each one that is used to provide the prefetch data in the CDS request.
 
 Prefetch tokens MUST be delimited by `{{` and `}}`, MUST be named based upon the field they correspond to, and MUST have a primitive value.