Update proxying-api-requests-in-development.md to use non-depricated format

Is your proposal related to a problem?

The guide in proxying-api-requests-in-development.md uses a depricated webpack format for creating a dev server. When developing locally, leads to warnings

Warnings:

Describe the solution you'd like

Update the example file to create a dev server without warnings (at the time of writing I don't know what that is).

Describe alternatives you've considered

Add a warning on the page saying this method of creating a dev server is depricated

Additional Context

Webpack middlewares has instructions on this