Support x-www-form-urlencoded

[hector-js]

Is your feature request related to a problem? Please describe.
Being able to generate a case supporting x-www-form-urlencoded requests

Describe the solution you'd like
If you dont specify any content-type, the library will work with json requests and reponse.
Adding the content-type as application/x-www-form-urlencoded will generated the resource file and test file based on this.