docs: add webpack 5 note on @project-serum/anchor (#1320)

ts/README.md

@@ -0,0 +1,10 @@
+# @project-serum/anchor
+
+[![npm](https://img.shields.io/npm/v/@project-serum/anchor.svg?color=blue)](https://www.npmjs.com/package/@project-serum/anchor)
+[![Docs](https://img.shields.io/badge/docs-typedoc-blue)](https://project-serum.github.io/anchor/ts/index.html)
+
+TypeScript client for Anchor programs.
+
+## Note
+
+* `@project-serum/anchor` depends on node.js native modules. Therefore, webpack 5 will not work with current version. You will either need to rollback to webpack 4, or use a polyfill for each missing dependency.