Fix import path for example provider

[lleon-uala]

Existing path is missing the name of the provider:

import { exampleRouter } from '../providers';

This should point to examples, otherwise it results in an error.

Backend failed to start up TypeError:
 _plugins_form_data__WEBPACK_IMPORTED_MODULE_11___default(...) is not a function

[nthings]

I think is best to add a index.ts file with all the exports on the providers folder that way you can have multiple providers into its own file for example some routes that call GitHub API and another one for AWS calls. https://github.com/premisedata/dynamic-data-form-extension/pull/20