Add mTLS support to library

[osadalakmal]

Currently we have a need for adding mTLS support to this library as we have it enabled on server side. This does not seem to be a big issue. Mostly it just needs to be passed from top level objects (Jira, Confluence, etc) down to request class and then on to the actuals python requests module. Would this be something that the maintainers and community be interested in? Would there be anything else to consider? I can submit a draft PR if folks think this is an ok idea to proceed on.

[gonchik]

Hi @osadalakmal , please submit a PR. for now I would say it's something in requests level should be updated