updated README file

Author: danielcosta

README.md

@@ -56,7 +56,13 @@ function setAction(Action $action) {
 - `__construct()` The constructor checks that the value exist in the enum
 - `__toString()` You can `echo $myValue`, it will display the enum value (value of the constant)
 - `getValue()` Returns the current value of the enum
-- `toArray()` (static) Returns an array of all possible values (constant name in key, constant value in value)
+- `getKey()` Returns the key of the current value on Enum
+- `keys()` (@static) Returns the names (keys) of all constants in the Enum class
+- `values()` (@static) method Returns all possible values as an array (constant name in key, constant value in value)
+- `toArray()` (@static and @deprecated) Alias for `values()`
+- `isValid()` (@static) Check if tested value is valid on enum set
+- `isValidKey()` (@static) Check if tested key is valid on enum set
+- `search()` Return key for searched value
 
 ### Static methods