Update references for the ChilliCream TimeSpan scalar (#66)

Author: glen-84

package.json

@@ -29,6 +29,13 @@
     "trailingComma": "none"
   },
   "cspell": {
-    "words": ["secfrac", "apollographql", "fullyear", "mday", "numoffset"]
+    "words": [
+      "ABNF",
+      "apollographql",
+      "fullyear",
+      "mday",
+      "numoffset",
+      "secfrac"
+    ]
   }
 }

scalars/contributed/chillicream/time-span.md

@@ -116,7 +116,5 @@ Invalid input values:
 
 # References
 
-- [ISO 8601](https://www.iso.org/iso-8601-date-and-time-format.html) — Date and
-  time format (includes duration format)
-- [ISO 8601 Durations](https://en.wikipedia.org/wiki/ISO_8601#Durations) —
-  Wikipedia reference for duration format
+- [RFC 3339 Appendix A](https://datatracker.ietf.org/doc/html/rfc3339#appendix-A)
+  — ABNF grammar for ISO 8601 durations