fix(react-icons): add sideEffects: false to dist/esm/package.json

The generated dist/esm/package.json only contains {"type": "module"},
which shadows the root package.json's "sideEffects": false declaration.
Webpack resolves the nearest package.json for each module, so all icons
under dist/esm/ are treated as having side effects, breaking tree-shaking
and bundling all 2846 icons (~7MB) regardless of usage.

Fixes #12313

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: logonoff

packages/react-icons/scripts/ensureEsmPackageJson.mjs

@@ -9,4 +9,4 @@ const esmPackageJsonPath = join(__dirname, '../dist/esm/package.json');
 mkdirSync(dirname(esmPackageJsonPath), { recursive: true });
 
 // Write package.json to mark ESM directory as a module
-writeFileSync(esmPackageJsonPath, JSON.stringify({ type: 'module' }, null, 2));
+writeFileSync(esmPackageJsonPath, JSON.stringify({ type: 'module', sideEffects: false }, null, 2));