Add missing javadoc

Author: lbalmaceda

lib/src/main/java/com/auth0/jwt/interfaces/JWTVerifier.java

@@ -2,6 +2,15 @@
 
 import com.auth0.jwt.exceptions.JWTVerificationException;
 
+
 public interface JWTVerifier {
+  
+  /**
+   * Performs the verification against the given Token
+   *
+   * @param token to verify.
+   * @return a verified and decoded JWT.
+   * @throws JWTVerificationException if any of the verification steps fail
+   */
   DecodedJWT verify(String token) throws JWTVerificationException;
 }