Extending docs development section with samples of how to test traffic to varnishes

[ziollek]

Description

Varnish machines are not exposed to the host machine in the local development environment, however, they are accessible from other dockers.

Enhancement

It would be beneficial to add a section to the documentation that describes:

• how to make a cURL request from for example uwsgi docker that will hit a particular varnish server
• how to check if the request is routed by a particular route defined in vaas