Adds DI and SPI examples

lang/src/main/java/annotations/jsonserializer/JsonSerializeException.java

@@ -1,7 +1,7 @@
 package annotations.jsonserializer;
 
 class JsonSerializeException extends RuntimeException {
-    JsonSerializeException(String message) {
-        super(message);
+    public JsonSerializeException(String message, Throwable cause) {
+        super(message, cause);
     }
 }

lang/src/main/java/annotations/jsonserializer/SerializableFieldExtractor.java

@@ -21,7 +21,7 @@ class SerializableFieldExtractor {
             }
             return jsonElements;
         } catch (SecurityException | IllegalArgumentException | IllegalAccessException e) {
-            throw new JsonSerializeException(e.getMessage());
+            throw new JsonSerializeException("JSON serializing error", e);
         }
     }