MPP / KJS: Fix incorrect source maps generating for ESM target

Author: aerialist7

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/targets/js/webpack/KotlinWebpackConfig.kt

@@ -211,7 +211,7 @@ data class KotlinWebpackConfig(
             """
                 // source maps
                 config.module.rules.push({
-                        test: /\.js${'$'}/,
+                        test: /\.m?js${'$'}/,
                         use: ["source-map-loader"],
                         enforce: "pre"
                 });