feat: upgrade ts target

tsconfig.json

@@ -4,7 +4,8 @@
     "noImplicitAny": false /* required for js files */,
     "strictNullChecks": false /* required for js files */,
     "outDir": "./dist",
-    "target": "es2018",
+    /* https://github.com/microsoft/TypeScript/wiki/Node-Target-Mapping */
+    "target": "es2020",
     "module": "commonjs",
     "sourceMap": true,
     "allowSyntheticDefaultImports": true,
@@ -14,7 +15,7 @@
     "noImplicitOverride": true,
     "experimentalDecorators": true,
     "useUnknownInCatchVariables": false /* we aren't prepared for enabling this by default since ts 4.4*/,
-    "lib": ["es2018"],
+    "lib": ["es2020"],
     "types": ["node", "jest", "jest-extended", "expect-more-jest"],
     "allowJs": true,
     "checkJs": true

tsconfig.strict.json

@@ -3,7 +3,7 @@
   "compilerOptions": {
     "strictNullChecks": true,
     "noImplicitAny": true,
-    "lib": ["es2019"]
+    "lib": ["es2020"]
   },
   "include": [
     "lib/config/app-strings.ts",