Add OpenQASM 3 support

[abhinavd]

OpenQASM 2 has some limitations, such as not being able to express parametrised circuits with unbound parameters. Being able to parse strings/files with the OpenQASM 3 spec would be a great way to get around this limitation.

[jcmgray]

Hi @abhinavd yes would be great support as many formats as possible and happy to accept PRs along these lines! Though I'd note I am probably unlikely to implement this myself any time soon.

[abhinavd]

No worries, thank you!