Adding isAxiosError typeguard documentation (#3767)

Co-authored-by: Jay <jasonsaayman@gmail.com>

README.md

@@ -826,10 +826,21 @@ axios depends on a native ES6 Promise implementation to be [supported](http://ca
 If your environment doesn't support ES6 Promises, you can [polyfill](https://github.com/jakearchibald/es6-promise).
 
 ## TypeScript
-axios includes [TypeScript](http://typescriptlang.org) definitions.
+
+axios includes [TypeScript](http://typescriptlang.org) definitions and a type guard for axios errors.
+
 ```typescript
-import axios from 'axios';
-axios.get('/user?ID=12345');
+let user: User = null;
+try {
+  const { data } = await axios.get('/user?ID=12345');
+  user = data.userDetails;
+} catch (error) {
+  if (axios.isAxiosError(error)) {
+    handleAxiosError(error);
+  } else {
+    handleUnexpectedError(error);
+  }
+}
 ```
 
 ## Online one-click setup