feat!: drop node 18

Author: sxzz

package.json

@@ -98,7 +98,7 @@
     "vitest": "^3.1.3"
   },
   "engines": {
-    "node": ">=18.12.0"
+    "node": ">=20.18.0"
   },
   "prettier": "@sxzz/prettier-config"
 }

tsdown.config.ts

@@ -1,9 +1,5 @@
 import { defineConfig } from 'tsdown'
 
 export default defineConfig({
-  entry: ['./src/*.ts'],
-  format: 'esm',
-  target: 'node18.12',
-  clean: true,
-  dts: { transformer: 'oxc' },
+  entry: './src/*.ts',
 })