build(package.json): update exports structure and add types definition

Author: J3m5

package.json

@@ -9,8 +9,16 @@
   "author": "Kévin Dunglas",
   "sideEffects": false,
   "type": "module",
-  "exports": "./lib/index.js",
+  "exports": {
+    ".": {
+      "types": "./lib/index.d.ts",
+      "import": "./lib/index.js",
+      "default": "./lib/index.js"
+    },
+    "./package.json": "./package.json"
+  },
   "main": "./lib/index.js",
+  "types": "./lib/index.d.ts",
   "files": [
     "*.md",
     "lib",