use ES modules

.config

@@ -1,4 +1,3 @@
 repo-owner = sanctuary-js
 repo-name = sanctuary-descending
 contributing-file = .github/CONTRIBUTING.md
-module-type = commonjs

.eslintrc.json

@@ -1,17 +1,18 @@
 {
   "root": true,
   "extends": ["./node_modules/sanctuary-style/eslint.json"],
+  "parserOptions": {"sourceType": "module"},
   "rules": {
     "comma-dangle": ["off"]
   },
   "overrides": [
     {
       "files": ["index.js"],
-      "globals": {"Deno": "readonly", "__doctest": "readonly", "define": "readonly", "module": "readonly", "process": "readonly", "require": "readonly", "self": "readonly"}
+      "globals": {"Deno": "readonly", "process": "readonly"}
     },
     {
       "files": ["test/**/*.js"],
-      "parserOptions": {"ecmaVersion": 2020, "sourceType": "module"}
+      "parserOptions": {"ecmaVersion": 2020}
     }
   ]
 }