feat(packages/platform): add global isClient util and build config

packages/platform/build.config.ts

@@ -0,0 +1,9 @@
+import { defineBuildConfig } from 'unbuild';
+
+export default defineBuildConfig({
+  rollup: {
+    esbuild: {
+        // minify: true,
+    },
+  },
+});