chore: update docs

Author: gabriel-logan

.idea/sonarlint/issuestore/1/d/1d784fce58c3719506730fb9749600554125b511

@@ -5,8 +5,32 @@
 
 ## JAVA
 
-How to use:
+## How to install
 
 follow the steps below to use the library in your project.
 
-https://jitpack.io/#multiform-validator/java/0.0.1
+https://jitpack.io/#multiform-validator/java/0.0.1
+
+## Example of how to use
+
+```java
+import io.github.multiform_validator.Validator;
+import io.github.multiform_validator.EmailValidator;
+import io.github.multiform_validator.CpfValidator;
+import io.github.multiform_validator.CnpjValidator;
+
+public class Main {
+    public static void main(String[] args) {
+        System.out.println(emailValidator.isEmail("foo@bar.com")); // true
+        System.out.println(emailValidator.isEmail("foo@bar")); // false
+
+        System.out.println(cpfValidator.cpfIsValid("123.456.789-09")); // true
+        System.out.println(cpfValidator.cpfIsValid("123.456.789-00")); // false
+        
+        System.out.println(cnpjValidator.cnpjIsValid("12.345.678/0001-09")); // true
+        System.out.println(cnpjValidator.cnpjIsValid("12.345.678/0001-00")); // false
+    }
+}
+```
+
+Lib is in development, there's other validators that you can use, but they are not yet documented.