Update README.md

Author: ota-meshi

README.md

@@ -121,6 +121,32 @@ For example:
 }
 ```
 
+For example, if you are using the `"@typescript-eslint/parser"`, and if you want to use TypeScript in `<script>` of `.svelte`, you need to add more `parserOptions` configuration.
+
+```js
+module.exports = {
+  // ...
+  parser: "@typescript-eslint/parser",
+  parserOptions: {
+    // ...
+    project: "path/to/your/tsconfig.json",
+    extraFileExtensions: [".svelte"], // This is a required setting in `@typescript-eslint/parser` v4.24.0.
+  },
+  overrides: [
+    {
+      files: ["*.svelte"],
+      parser: "svelte-eslint-parser",
+      // Parse the `<script>` in `.svelte` as TypeScript by adding the following configuration.
+      parserOptions: {
+        parser: "@typescript-eslint/parser",
+      },
+    },
+    // ...
+  ],
+  // ...
+}
+```
+
 #### Multiple parsers
 
 If you want to switch the parser for each lang, specify the object.