docs(zod-validator): add usage docs for `zErrValidator` (#900)

* docs(zod-validator): add usage docs for `zErrValidator`, throw a validating error instead of directly returning an error response. (#890)

* docs(zod-validator): change zod error to Hono HTTPException

* remove useless generic

packages/zod-validator/README.md

@@ -37,6 +37,32 @@ app.post(
 )
 ```
 
+Throw Error:
+
+throw a zod validate error instead of directly returning an error response.
+
+```ts
+// file: validator-wrapper.ts
+import { ZodSchema } from "zod";
+import type { ValidationTargets } from "hono";
+import { zValidator as zv } from "@hono/zod-validator";
+
+export const zValidator = (target: keyof ValidationTargets,  schema: ZodSchema) => 
+zv(target, schema, (result, c) => {
+  if (!result.success) {
+    throw new HTTPException(400, { cause: result.error });
+  }
+})
+
+// usage
+import { zValidator } from './validator-wrapper'
+app.post(
+  '/post',
+  zValidator('json', schema)
+  //...
+)
+```
+
 ## Author
 
 Yusuke Wada <https://github.com/yusukebe>