chore(custom): tsconfig target set "es5"

packages/toolkit/tsconfig.json

@@ -11,7 +11,7 @@
     // "disableReferencedProjectLoad": true,             /* Reduce the number of projects loaded automatically by TypeScript. */
 
     /* Language and Environment */
-    "target": "es6",                                  /* Set the JavaScript language version for emitted JavaScript and include compatible library declarations. */
+    "target": "es5",                                  /* Set the JavaScript language version for emitted JavaScript and include compatible library declarations. */
      "lib": ["esnext", "DOM"],                                        /* Specify a set of bundled library declaration files that describe the target runtime environment. */
     // "jsx": "preserve",                                /* Specify what JSX code is generated. */
     // "experimentalDecorators": true,                   /* Enable experimental support for TC39 stage 2 draft decorators. */