feat(loader): Refactor loaders and metadata.

providers/yaml/src/test/java/sample/Sample.java

@@ -0,0 +1,17 @@
+package sample;
+
+import cc.carm.lib.configuration.EasyConfiguration;
+
+public class Sample {
+
+    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.INFO.NAME.getNotNull() + " !");
+    }
+
+}