Add ref

spec.bs

@@ -37,6 +37,9 @@ spec: RFC6234; urlPrefix: https://www.ietf.org/rfc/rfc6234.txt
 urlPrefix: https://datatracker.ietf.org/doc/html/rfc8032
   type: dfn
     text: verify; url: section-5.1.7
+urlPrefix: https://datatracker.ietf.org/doc/html/rfc3986
+  type:dfn
+    text: unreserved percent encoding character; url: section-2.3
 spec: html; urlPrefix: https://html.spec.whatwg.org/C
   type: dfn
     text: create an agent; url: create-an-agent
@@ -3476,7 +3479,7 @@ Each {{InterestGroupReportingScriptRunnerGlobalScope}} has a
   |value|)</dfn> method steps are:
   1. [=list/For each=] [=code unit=] |c| in |name| and |value|:
      1. [=exception/Throw=] a {{TypeError}} if both of the following conditions hold:
-        * |c| is not an unreserved percent encoding character
+        * |c| is not an [=unreserved percent encoding character=]
         * |c| is not `%`
 
   1. [=map/Set=] [=this=]'s [=relevant global object=]'s