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

@@ -1,13 +1,18 @@
 {
   "root": true,
   "extends": ["./node_modules/sanctuary-style/eslint.json"],
+  "parserOptions": {"sourceType": "module"},
   "rules": {
     "comma-dangle": ["off"]
   },
   "overrides": [
     {
       "files": ["*.md"],
-      "globals": {"$": "readonly", "Descending": "readonly", "S": "readonly", "Z": "readonly"}
+      "globals": {"$": "readonly", "Descending": "readonly", "S": "readonly", "Useless": "readonly", "Z": "readonly"},
+      "rules": {
+        "no-unused-vars": ["error", {"varsIgnorePattern": "^([$]|S|Useless)$"}],
+        "semi": ["off"]
+      }
     },
     {
       "files": ["index.js"],
@@ -18,7 +23,7 @@
     },
     {
       "files": ["test/**/*.js"],
-      "parserOptions": {"ecmaVersion": 2020, "sourceType": "module"}
+      "parserOptions": {"ecmaVersion": 2020}
     }
   ]
 }

.gitignore

@@ -1,3 +1,2 @@
-/.nyc_output/
 /coverage/
 /node_modules/