Apply stricter ESM rules

Closes $61.

.eslintrc

@@ -1,9 +1,15 @@
 {
 	"root": true,
 	"extends": ["./index.js", "eslint-config-prettier"],
-	"plugins": ["eslint-plugin-prettier", "eslint-plugin-unicorn"],
+	"plugins": [
+		"eslint-plugin-prettier",
+		"eslint-plugin-unicorn",
+		"eslint-plugin-import"
+	],
 	"rules": {
-		"prettier/prettier": 1
+		"prettier/prettier": 1,
+		"unicorn/prefer-module": 0,
+		"import/no-commonjs": 0
 	},
 	"ignorePatterns": ["test/fixtures/*.config.*"],
 	"overrides": [

index.js

@@ -526,7 +526,7 @@ module.exports = {
 		'import/no-self-import': 2,
 		'import/export': 2,
 		'import/no-mutable-exports': 2,
-		'import/no-commonjs': 1,
+		'import/no-commonjs': 2,
 		'import/no-amd': 1,
 		'import/exports-last': 2,
 		'import/no-namespace': 1,
@@ -562,7 +562,7 @@ module.exports = {
 		'import/no-named-export': 0,
 		'import/no-unused-modules': 0,
 		'unicorn/prefer-export-from': 0,
-		'unicorn/prefer-module': 1,
+		'unicorn/prefer-module': 2,
 		'n/file-extension-in-import': 0,
 		'import/extensions': [2, 'always', { ignorePackages: true }],
 		'import/consistent-type-specifier-style': 0,

test/.eslintrc

@@ -3,5 +3,10 @@
 	"parserOptions": {
 		"ecmaVersion": 2022,
 		"sourceType": "module"
+	},
+	"plugins": ["eslint-plugin-unicorn", "eslint-plugin-import"],
+	"rules": {
+		"unicorn/prefer-module": 2,
+		"import/no-commonjs": 2
 	}
 }