Add ESM support, fallback to CommonJS

package.json

@@ -16,7 +16,17 @@
   "engines": {
     "node": ">=22"
   },
-  "main": "./build/index.js",
+  "type": "module",
+  "main": "./build/cjs/index.js",
+  "module": "./build/esm/index.js",
+  "types": "./build/esm/index.d.ts",
+  "exports": {
+    ".": {
+      "require": "./build/cjs/index.js",
+      "import": "./build/esm/index.js",
+      "types": "./build/esm/index.d.ts"
+    }
+  },
   "license": "MIT",
   "author": {
     "name": "Kamil Mielnik",
@@ -34,15 +44,14 @@
   "files": [
     "build/**"
   ],
-  "types": "./build/index.d.ts",
   "np": {
     "yarn": false
   },
   "publishConfig": {
     "access": "public"
   },
   "scripts": {
-    "build": "tsc --project .",
+    "build": "tsc --project . && tsc --project tsconfig.cjs.json",
     "build:docs": "typedoc",
     "clean": "rimraf build coverage docs",
     "postbuild": "npm run build:docs",

tsconfig.cjs.json

@@ -0,0 +1,21 @@
+{
+  "compilerOptions": {
+    "declaration": true,
+    "downlevelIteration": true,
+    "esModuleInterop": true,
+    "forceConsistentCasingInFileNames": true,
+    "lib": ["esnext"],
+    "module": "commonjs",
+    "moduleResolution": "node",
+    "noImplicitReturns": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "outDir": "./build/cjs",
+    "resolveJsonModule": true,
+    "rootDir": "./src",
+    "strict": true,
+    "target": "esnext"
+  },
+  "exclude": ["node_modules", "**/*.test.ts"],
+  "include": ["./src", "index.ts"]
+}

tsconfig.json

@@ -5,12 +5,12 @@
     "esModuleInterop": true,
     "forceConsistentCasingInFileNames": true,
     "lib": ["esnext"],
-    "module": "commonjs",
+    "module": "esnext",
     "moduleResolution": "node",
     "noImplicitReturns": true,
     "noUnusedLocals": true,
     "noUnusedParameters": true,
-    "outDir": "./build",
+    "outDir": "./build/esm",
     "resolveJsonModule": true,
     "rootDir": "./src",
     "strict": true,