add injection prototype (#140)

* add injection prototype

spec/src/main/asciidoc/02-config.adoc

@@ -3,3 +3,28 @@
 == Introduction
 
 
+== Support Injection
+A ConfigMapping interface can be injected via the `@Inject`. The following example demonstrates the usage.
+
+[source]
+----
+customer.name=Bob
+customer.age=28
+----
+
+[Usage example]
+
+The following is a usage example for how `@Inject` may be used:
+
+[source, java]
+----
+@ConfigMapping("customer")
+public interface MyConfigMapping{
+    String name;
+    int age;
+}
+
+@Inject MyConfigMapping myConfigMapping;
+----
+
+In the above example, the values for `myConfigMapping.name` for `myConfigMapping.age` will be `Bob`, `28` correspondingly.