feat: add an error code for email already verified

Author: pash2048

Diff for: src/ParseError.js

@@ -433,6 +433,15 @@ ParseError.EMAIL_MISSING = 204;
  */
 ParseError.EMAIL_NOT_FOUND = 205;
 
+/**
+ * Error code indicating that the email has already been verified and can not be verified again.
+ *
+ * @property {number} EMAIL_ALREADY_VERIFIED
+ * @static
+ */
+ParseError.EMAIL_ALREADY_VERIFIED = 212;
+
+
 /**
  * Error code indicating that a user object without a valid session could
  * not be altered.