feat: adding JSON overview and Json configuration docs (#3102)

* feat: adding JSON overview and Json configuration docs

* update: implementing first round of review comments

* feat: adding page for io serialization and implementing review comments

* update: created new page for I/O serialization

* update: implementing additional review comments

* update: small update to section ordering

* update: implementing comments related to the IO sources page

* update: small additional updates for streams and minor update to json config

* update: implementing TWr review comments from Danil and adding example ids

* fix: last minor TWr review changes

Author: daniCsorbaJB

docs-website/serialization.tree

@@ -13,6 +13,7 @@
             <toc-element topic="serialization-json-configuration.md"/>
             <toc-element topic="serialization-json-elements.md"/>
             <toc-element topic="serialization-transform-json.md" toc-title="JSON transformation"/>
+            <toc-element topic="serialization-json-io-sources.md"/>
         </toc-element>
         <toc-element topic="serialization-polymorphism.md"/>
         <toc-element toc-title="Custom serializers">

docs-website/topics/configure-json-serialization.md

@@ -0,0 +1,85 @@
+[//]: # (title: JSON serialization overview)
+
+The Kotlin serialization library allows you to easily convert Kotlin objects to JSON and back.
+The [`Json`](https://kotlinlang.org/api/kotlinx.serialization/kotlinx-serialization-json/kotlinx.serialization.json/-json/) class is the primary tool for this, offering flexibility in how JSON is generated and parsed.
+You can configure `Json` instances to handle specific JSON behaviors or use its default instance for basic tasks.
+
+With the `Json` class, you can:
+
+* Serialize Kotlin objects to JSON strings using the [`encodeToString()`](https://kotlinlang.org/api/kotlinx.serialization/kotlinx-serialization-json/kotlinx.serialization.json/-json/encode-to-string.html) function.
+* Deserialize JSON strings back to Kotlin objects with the [`decodeFromString()`](https://kotlinlang.org/api/kotlinx.serialization/kotlinx-serialization-json/kotlinx.serialization.json/-json/decode-from-string.html) function.
+* [Work directly with the `JsonElement`](serialization-json-elements.md) when handling complex JSON structures using the [`encodeToJsonElement()`](https://kotlinlang.org/api/kotlinx.serialization/kotlinx-serialization-json/kotlinx.serialization.json/encode-to-json-element.html) and the [`decodeFromJsonElement()`](https://kotlinlang.org/api/kotlinx.serialization/kotlinx-serialization-json/kotlinx.serialization.json/decode-from-json-element.html) functions.
+* Use [Experimental](components-stability.md#stability-levels-explained) extension functions to [serialize and deserialize I/O sources](serialization-json-io-sources.md) without creating intermediate strings, including JVM streams as well as [`kotlinx-io`](https://github.com/Kotlin/kotlinx-io) and [Okio](https://square.github.io/okio/) types.
+
+Before you start, import the following declarations from the serialization library:
+
+```kotlin
+import kotlinx.serialization.*
+import kotlinx.serialization.json.*
+```
+
+Here's a simple example that uses the default `Json` instance to show how JSON serialization works in Kotlin:
+
+```kotlin
+// Imports declarations from the serialization library
+import kotlinx.serialization.*
+import kotlinx.serialization.json.*
+
+//sampleStart
+@Serializable
+data class User(val name: String, val age: Int)
+
+fun main() {
+    // Uses the default Json instance
+    val json = Json
+
+    // Creates a User object
+    val user = User("Alice", 30)
+
+    // Converts the User object to a JSON string
+    val jsonString = json.encodeToString(user)
+    println(jsonString)
+    // {"name":"Alice","age":30}
+
+    // Converts the JSON string back to a User object
+    val deserializedUser = json.decodeFromString<User>(jsonString)
+    println(deserializedUser)
+    // User(name=Alice, age=30)
+//sampleEnd
+}
+```
+{kotlin-runnable="true" id="first-json-example"}
+
+In addition to using the default configuration, you can [customize the `Json` instance](serialization-json-configuration.md) for specific use cases,
+such as ignoring unknown keys:
+
+```kotlin
+// Imports declarations from the serialization library
+import kotlinx.serialization.*
+import kotlinx.serialization.json.*
+
+//sampleStart
+@Serializable
+data class Project(val name: String)
+
+// Configures a Json instance to ignore unknown keys
+val customJson = Json {
+    ignoreUnknownKeys = true
+}
+
+fun main() {
+    val data = customJson.decodeFromString<Project>("""
+        {"name":"kotlinx.serialization","language":"Kotlin"}
+    """)
+    println(data)
+    // Project(name=kotlinx.serialization)
+}
+//sampleEnd
+```
+{kotlin-runnable="true" id="first-json-instance-example"}
+
+## What's next
+
+* Learn how to [customize `Json` instances](serialization-json-configuration.md) to address different use cases for serialization and deserialization.
+* Explore [advanced JSON element handling](serialization-json-elements.md) to manipulate and work with JSON data before it is parsed or serialized.
+* Discover how to [transform JSON during serialization and deserialization](serialization-transform-json.md) for more control over your data.