[Quick start Example] Adding RoR quick start example to Tracetest

[danielbdias]

This PR adds a simple example of a Tracetest test running against a Ruby on Rails API

Changes

• Add quick-start-ruby-on-rails folder on ./examples

Fixes

• Craft sample quick start apps in Ruby for Rails and Sinatra #2249

Checklist

• tested locally
• added new dependencies
• updated the docs
• added a test

[xoscar]

I'm getting a similar issue running this and running the Sinatra version, it throws a required error, Could it be because we are not installing the dependencies when creating the docker image?

[xoscar]

LGTM!