Added link

Author: webron

versions/3.0.md

@@ -2617,7 +2617,7 @@ The following properties are taken directly from the JSON Schema definition and
 - exclusiveMinimum
 - maxLength
 - minLength
-- pattern (This string SHOULD be a valid regular expression, according to the ECMA 262 regular expression dialect)
+- pattern (This string SHOULD be a valid regular expression, according to the [ECMA 262 regular expression](https://www.ecma-international.org/ecma-262/5.1/#sec-7.8.5) dialect)
 - maxItems
 - minItems
 - uniqueItems