docs: clarify yupResolver context usage in README

Author: eotkd4791

README.md

@@ -147,6 +147,19 @@ Dead simple Object schema validation.
 
 [![npm](https://img.shields.io/bundlephobia/minzip/yup?style=for-the-badge)](https://bundlephobia.com/result?p=yup)
 
+> ⚠️ Pass context via `useForm({ context })`, not via `yupResolver`'s `schemaOptions`. Using React state/atoms via `schemaOptions.context` can result in stale/undefined values.
+
+```typescript jsx
+// Correct
+useForm({
+  resolver: yupResolver(schema),
+  context: { foo: true },
+});
+
+// Avoid - context will be stale/undefined
+yupResolver(schema, { context: { foo: true } });
+```
+
 ```typescript jsx
 import { useForm } from 'react-hook-form';
 import { yupResolver } from '@hookform/resolvers/yup';