Add QASM output

[Renmusxd]

Add support for writing qasm files from the generated circuits.

[AthenaCaesura]

Hello! Any chance I can pick this one up? I'm looking to learn some rust in my week off and this seems like a nice project to contribute to.

[Renmusxd]

Hi! Thanks, I'll happily take PRs for this! I'm on vacation for a few more days, hence the delay in responding, but will be able to engage with code review once I get back.

[zxq82lm]

See #54.