Add example usage to README

Signed-off-by: trivernis <trivernis@protonmail.com>

README.md

@@ -13,7 +13,7 @@ type that implements it. This trait can be derived if the `derive` **feature** i
 
 ```rust
 
-use rusty_value::RustyValue;
+use rusty_value::{RustyValue, Value};
 
 #[derive(RustyValue)]
 struct MyStruct {
@@ -22,10 +22,26 @@ struct MyStruct {
 }
 
 fn main() {
-  MyStruct {
+  let value = MyStruct {
     foo: "Hello World".to_string(),
     bar: 12,
   }.into_rusty_value();
+
+  match value {
+      Value::Primitive(p) => match p {
+          rusty_value::Primitive::Integer(_) => println!("is an integer"),
+          rusty_value::Primitive::Float(_) => println!("is a float"),
+          rusty_value::Primitive::String(_) => println!("is a string"),
+          rusty_value::Primitive::OsString(_) => println!("is a os string"),
+          rusty_value::Primitive::Char(_) => println!("is a char"),
+          rusty_value::Primitive::Bool(_) => println!("is a boolean"),
+      },
+      Value::Struct(s) => println!("is a struct with name {}", s.name),
+      Value::Enum(e) => println!("is an enum with name {} of variant {}", e.name, e.variant),
+      Value::Map(_) => println!("is a map"),
+      Value::List(_) => println!("is a list"),
+      Value::None => println!("is none"),
+  }
 }
 ```