Added json.md - Serialization part

Signed-off-by: Jai2305 <jainjai2305@gmail.com>

guides/json.md

@@ -0,0 +1,59 @@
+- [Working with Json](#working-with-json)
+  - [Serialization](#serialization)
+    - [Using toJsonString method](#using-tojsonstring-method)
+    - [Manual serialization](#manually-serialize-by-providing-mapper-and-generator)
+
+
+# Working with Json
+
+OpenSearch Java client seamlessly integrate with JSON providing serialization and deserialization capability.
+
+## Serialization
+
+For demonstration let's consider an instance of `SearchRequest`.
+
+```java
+public static void main(final String[] args) {
+  SearchRequest searchRequest = SearchRequest.of(
+          request -> request.index("index1", "index2")
+                  .aggregations(Collections.emptyMap())
+                  .terminateAfter(5L)
+                  .query(q -> q.match(t -> t.field("name").query(FieldValue.of("OpenSearch"))))
+  );
+}
+
+```
+### Using toJsonString method
+For classes implementing `PlainJsonSerializable`, which extends `JsonpSerializable`, a default `toJsonString` method is provided. 
+This method utilizes the default mapper and generator from the JsonpUtils class within the package to streamline the serialization process.
+
+The following code example demonstrates how to use the `toJsonString` method to serialize objects:
+
+```java
+String requestString = searchRequest.toJsonString();
+```
+
+
+### Manually serialize by providing mapper and generator
+For classes implementing the `JsonpSerializable` interface, a serialize method is provided, which takes a mapper and a generator 
+as arguments and returns the JSON string representation of the instance.
+
+The following sample code demonstrates how to serialize an instance of a Java class:
+
+```java
+private String toJson(JsonpSerializable object) {
+  try (StringWriter writer = new StringWriter()) {
+    JsonbJsonpMapper mapper = new JsonbJsonpMapper();
+    try (JsonGenerator generator = mapper.jsonProvider().createGenerator(writer)) {
+      serialize(generator, mapper);
+    }
+    return writer.toString();
+  } catch (IOException ex) {
+    throw new UncheckedIOException(ex);
+  }
+}
+
+```
+
+
+