chore: update ts target from es6 to es2018

Author: Aetherinox

tsconfig.json

@@ -4,7 +4,7 @@
     "inlineSourceMap": true,
     "inlineSources": true,
     "module": "ESNext",
-    "target": "es6",
+    "target": "ES2018",
     "allowJs": true,
     "noImplicitAny": true,
     "moduleResolution": "node",
@@ -26,4 +26,4 @@
     "**/*.ts"
   ],
   "exclude": [".vscode"]
-}
+}