Add integration tests demonstrating real-world JSON5 serialization usage

- Test complex data structures with maps, lists, and nested objects
- Verify JSON5-specific features work in practice (comments, trailing commas)
- Demonstrate end-to-end serialization/deserialization workflow

Co-authored-by: hossain-khan <[email protected]>

Author: Copilot

lib/src/test/kotlin/io/github/json5/kotlin/JSON5IntegrationTest.kt

@@ -0,0 +1,71 @@
+package io.github.json5.kotlin
+
+import io.kotest.matchers.shouldBe
+import kotlinx.serialization.Serializable
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.DisplayName
+
+/**
+ * Simple integration test to verify end-to-end functionality
+ */
+@DisplayName("JSON5 Integration Test")
+class JSON5IntegrationTest {
+
+    @Serializable
+    data class Config(
+        val appName: String,
+        val version: Int,
+        val features: List<String>,
+        val settings: Map<String, String>
+    )
+
+    @Test
+    fun `should work with real-world example`() {
+        val config = Config(
+            appName = "MyApp",
+            version = 2,
+            features = listOf("auth", "analytics"),
+            settings = mapOf("theme" to "dark", "lang" to "en")
+        )
+        
+        // Serialize to JSON5
+        val json5 = JSON5.encodeToString(Config.serializer(), config)
+        
+        // Verify it's valid JSON5 format
+        json5 shouldBe "{appName:'MyApp',version:2,features:['auth','analytics'],settings:{theme:'dark',lang:'en'}}"
+        
+        // Deserialize back 
+        val decoded = JSON5.decodeFromString(Config.serializer(), json5)
+        
+        // Should be identical
+        decoded shouldBe config
+    }
+
+    @Test
+    fun `should handle JSON5 with comments and formatting`() {
+        val json5WithComments = """
+            {
+                // Application configuration
+                appName: 'MyApp',
+                version: 2, // current version
+                features: [
+                    'auth',
+                    'analytics', // trailing comma OK
+                ],
+                settings: {
+                    theme: 'dark',
+                    lang: 'en',
+                }
+            }
+        """.trimIndent()
+        
+        val config = JSON5.decodeFromString(Config.serializer(), json5WithComments)
+        
+        config shouldBe Config(
+            appName = "MyApp",
+            version = 2,
+            features = listOf("auth", "analytics"),
+            settings = mapOf("theme" to "dark", "lang" to "en")
+        )
+    }
+}