Feature request: Pass in yaml from stdin instead of file

[Amndeep7]

Use case: I have a few different Jira projects hosted by the same Jira instance. I want to be able to generate outputs on the fly depending on user request for graph / project combos. Instead of having to do a bunch of file io to have a template ready and then fill it out before calling this library/cli tool, I'd like to instead just pass in a string containing the yaml through stdin.