use ECMAScript 2021

.eslintrc.json

@@ -5,7 +5,7 @@
     },
     "extends": "eslint:recommended",
     "parserOptions": {
-        "ecmaVersion": 12,
+        "ecmaVersion": 2021,
         "sourceType": "module"
     },
     "rules": {

process_static

@@ -15,7 +15,7 @@ for file in static_tmp/**/*.@(json|webmanifest); do
 done
 
 find static_tmp -name '*.css' -exec csso {} -o {} \;
-find static_tmp -name '*.js' -exec terser --module -cmo {} {} \;
+find static_tmp -name '*.js' -exec terser --ecma 2021 --module -cmo {} {} \;
 
 replace=""
 for file in static_tmp/**/*.css static_tmp/js/*.js static_tmp/mask-icon.svg; do