update README.

Author: SimY4

README.md

@@ -128,7 +128,7 @@ Use the provided `CoregexInstances` trait to constrain string arbitraries:
 
 ```scala
 object MySpecification extends Properties("MySpecification") with CoregexInstances {
-  property("my property") = forAll { (str: String Matching "[a-zA-Z]{3}") =>
+  property("my property") = forAll { (str: StringMatching["[a-zA-Z]{3}"]) =>
     3 == str.length  
   }
 }

scalacheck/src/test/scala-2.13+/com/github/simy4/coregex/scalacheck/CoregexSpecification.scala

@@ -42,7 +42,8 @@ object CoregexSpecification extends Properties("Coregex") with CoregexInstances
 
   property("should generate matching ISO-8601 date string") = forAll {
     (iso8601Date: StringMatching[
-      "[12]\\d{3}-(?:0[1-9]|1[012])-(?:0[1-9]|1\\d|2[0-8])T(?:1\\d|2[0-3]):[0-5]\\d:[0-5]\\d(\\.\\d{2}[1-9])?Z"]) =>
+      "[12]\\d{3}-(?:0[1-9]|1[012])-(?:0[1-9]|1\\d|2[0-8])T(?:1\\d|2[0-3]):[0-5]\\d:[0-5]\\d(\\.\\d{2}[1-9])?Z"
+    ]) =>
       val formatter = DateTimeFormatter.ISO_INSTANT
       (iso8601Date: String) =? formatter.format(formatter.parse(iso8601Date))
   }