Created a new exception for mismatched mod versions.

src/main/java/dev/micle/loginprotection/network/MismatchedVersionException.java

@@ -0,0 +1,7 @@
+package dev.micle.loginprotection.network;
+
+public class MismatchedVersionException extends RuntimeException {
+    public MismatchedVersionException(String msg) {
+        super(msg);
+    }
+}