switch build to tsdown

package.json

@@ -2,22 +2,19 @@
   "name": "@jwetzell/posistagenet",
   "version": "2.1.1",
   "description": "",
-  "main": "./dist/cjs/index.js",
-  "module": "./dist/esm/index.js",
-  "types": "./dist/types/index.d.ts",
+  "main": "./dist/index.cjs",
+  "module": "./dist/index.mjs",
+  "types": "./dist/index.d.cts",
   "exports": {
     ".": {
-      "import": "./dist/esm/index.js",
-      "require": "./dist/cjs/index.js",
-      "types": "./dist/types/index.d.ts"
-    }
+      "import": "./dist/index.mjs",
+      "require": "./dist/index.cjs"
+    },
+    "./package.json": "./package.json"
   },
   "scripts": {
     "prebuild": "rimraf dist",
-    "build": "npm run build:cjs && npm run build:esm && npm run build:types",
-    "build:cjs": "tsc -p tsconfig.cjs.json && echo '{\"type\": \"commonjs\"}' > dist/cjs/package.json",
-    "build:esm": "tsc -p tsconfig.esm.json && echo '{\"type\": \"module\"}' > dist/esm/package.json",
-    "build:types": "tsc -p tsconfig.types.json",
+    "build": "tsdown",
     "example:client": "node examples/psn_client.js",
     "example:server": "node examples/psn_server.js",
     "prepublishOnly": "npm run build",
@@ -46,6 +43,7 @@
     "globals": "17.6.0",
     "prettier": "3.8.3",
     "rimraf": "6.1.3",
+    "tsdown": "0.22.0",
     "typescript": "5.9.3",
     "typescript-eslint": "8.59.1"
   }