docs(sample): Add sample codes. 🥚

README.md

@@ -45,6 +45,30 @@ Check out some code demonstrations [HERE](demo/src/main/java/cc/carm/lib/configu
 
 For more examples, see the [Development Guide](.doc/README.md).
 
+```java
+public class Sample {
+
+    @HeaderComment("Configurations for sample")
+    interface SampleConfig extends Configuration {
+        @HeaderComment("Configure your name!") // Header comment
+        ConfiguredValue<String> NAME = ConfiguredValue.of("Joker");
+        @InlineComment("Enabled?") // Inline comment
+        ConfiguredValue<Boolean> ENABLED = ConfiguredValue.of(true);
+    }
+
+    public static void main(String[] args) {
+        // 1. Make a configuration provider from a file.
+        ConfigurationProvider<?> provider = EasyConfiguration.from("config.yml");
+        // 2. Initialize the configuration classes or instances.
+        provider.initialize(SampleConfig.class);
+        // 3. Enjoy using the configuration!
+        SampleConfig.ENABLED.set(false);
+        System.out.println("Your name is " + SampleConfig.NAME.getNotNull() + " !");
+    }
+
+}
+```
+
 ### Dependencies
 
 #### Maven Dependency