rename JsType inheritors, add close method to JavaScriptEngine

Author: Tetraquark

javascript/src/commonMain/kotlin/dev/icerock/moko/javascript/JavaScriptEngine.kt

@@ -5,5 +5,15 @@
 package dev.icerock.moko.javascript
 
 expect class JavaScriptEngine() {
+    /**
+     * Evaluate some [script] with external [context].
+     *
+     * @throws JavaScriptEvaluationException in case of an error in the engine evaluation
+     */
     fun evaluate(context: Map<String, JsType>, script: String): JsType
+
+    /**
+     * Closes the engine and releases the allocated memory.
+     */
+    fun close()
 }

javascript/src/commonMain/kotlin/dev/icerock/moko/javascript/JsType.kt

@@ -4,10 +4,17 @@
 
 package dev.icerock.moko.javascript
 
+import kotlinx.serialization.json.JsonElement
+
 sealed class JsType {
-    data class Boolean(val value: Boolean): JsType
-    data class String(val value: String): JsType
-    data class Int(val value: Int): JsType
-    data class Double(val value: Double): JsType
-    data class Json(val value: JsonElement): JsType
+    data class Bool(val value: Boolean): JsType()
+    data class Str(val value: String): JsType()
+    data class IntNum(val value: Int): JsType()
+    data class DoubleNum(val value: Double): JsType()
+    data class Json(val value: JsonElement): JsType()
+
+    /**
+     * For "undefined" and "null".
+     */
+    object Null : JsType()
 }