fix: remove import assert for older node.js

Author: tkskto

rollup.config.js rollup.config.mjsrollup.config.js renamed to rollup.config.mjs

@@ -3,7 +3,12 @@ import commonjs from '@rollup/plugin-commonjs';
 import {nodeResolve} from '@rollup/plugin-node-resolve';
 import json from '@rollup/plugin-json';
 import terser from '@rollup/plugin-terser';
-import pkg from './package.json' assert {type: 'json'};
+import { readFile } from 'fs/promises';
+const pkg = JSON.parse(
+  await readFile(
+    new URL('./package.json', import.meta.url)
+  )
+);
 
 let dependencies = '';