Merge pull request #613 from snyk/fix/upgrade-ts-target

fix: upgrade Typescript target

Author: adrobuta

tsconfig.json

@@ -2,8 +2,8 @@
   "compilerOptions": {
     "pretty": true,
     /* Basic Options */
-    "target": "es2017",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017','ES2018' or 'ESNEXT'. */
-    "lib": ["es2017", "dom"],
+    "target": "es2018",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017','ES2018' or 'ESNEXT'. */
+    "lib": ["es2018", "dom"],
     "module": "commonjs",                     /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */
     // "allowJs": true,                          /* Allow javascript files to be compiled. */
     // "checkJs": true,                       /* Report errors in .js files. */