Refactor: Align with espree re: ESM

.eslintrc.json

@@ -1,11 +1,22 @@
 {
     "extends": "eslint",
+    "env": {
+        "es2020": true
+    },
     "parserOptions": {
         "sourceType": "module",
         "ecmaVersion": "2020"
     },
     "env": {
         "es6": true,
         "node": true
-    }
+    },
+    "overrides": [
+        {
+            "files": ["*.cjs"],
+            "parserOptions": {
+                "sourceType": "script"
+            }
+        }
+    ]
 }

package.json

@@ -5,10 +5,14 @@
   "type": "module",
   "main": "dist/eslint-visitor-keys.cjs",
   "exports": {
-    ".": {
-      "import": "./lib/index.js",
-      "require": "./dist/eslint-visitor-keys.cjs"
-    },
+    ".": [
+      {
+        "import": "./lib/index.js",
+        "require": "./dist/eslint-visitor-keys.cjs",
+        "default": "./dist/eslint-visitor-keys.cjs"
+      },
+      "./dist/eslint-visitor-keys.cjs"
+    ],
     "./package.json": "./package.json"
   },
   "files": [

rollup.config.js

@@ -1,9 +1,11 @@
 export default {
     input: "./lib/index.js",
     external: ["fs"],
+    treeshake: false,
     output: {
         exports: "default",
         format: "cjs",
-        file: "dist/eslint-visitor-keys.cjs"
+        file: "dist/eslint-visitor-keys.cjs",
+        sourcemap: true
     }
 };