Support custom headers via config

[Diizzayy]

Hello, I would like to know if there is a possibility to include other parameters in the headers through the client configuration, for cases where custom headers are needed to read the API schema.

Thanks in advance!

Originally posted by @douglasgusson in #87 (comment)

Hello, @Diizzayy, thanks for the answer.

My application is multitenancy. So, when I make a request, is needed to put an special header to specify what tenant I want to download the API schema. So, I would be greatfull if you allow to put it on requests. If you preffer, I can make a PR.

Originally posted by @douglasgusson in #87 (comment)

[Diizzayy]

Resolved in #132