Add docs for httpResolverOptions

Author: Kasim Ahmic

docs/rtk-query/usage/code-generation.mdx

@@ -108,6 +108,7 @@ interface SimpleUsage {
     | Array<string | RegExp | EndpointMatcherFunction>
   endpointOverrides?: EndpointOverrides[]
   flattenArg?: boolean
+  httpResolverOptions?: SwaggerParser.HTTPResolverOptions
 }
 
 export type EndpointMatcherFunction = (
@@ -169,3 +170,24 @@ const config: ConfigFile = {
   },
 }
 ```
+
+#### Custom HTTP resolver options
+
+If you need to customize the HTTP request issued to your server, you user the `httpResolverOptions` option. This object is passed directly to the `SwaggerParser` instance that fetches the OpenAPI schema.
+
+For example, you can pass custom headers or set a custom request timeout.
+
+```ts no-transpile title="openapi-config.ts"
+const config: ConfigFile = {
+  schemaFile: 'https://petstore3.swagger.io/api/v3/openapi.json',
+  apiFile: './src/store/emptyApi.ts',
+  outputFile: './src/store/petApi.ts',
+  httpResolverOptions: {
+    timeout: 30_000,
+    headers: {
+      Accept: 'application/json',
+      Authorization: 'Basic cmVkdXgtdG9vbGtpdDppcy1ncmVhdA==',
+    },
+  },
+}
+```