Add a interceptor rule/mock response even if the request isn't listed

[amitmbee]

Currently, we are able to mock/intercept only those requests which are already listened/listed on the UI. We could implement a Add button which opens up a input which prompts the user for URL and a method. Once that is provided, we could allow the extension to mock the requests with a custom used provided response, content-type and status-code.

[amitmbee]

#133