Add headers exchange type

[gordoneliel]

Adds headers exchange type when declaring an exchange

Description

GenRMQ currently supports the 3 predefined exchange types on AMPQ, but its missing the "headers" exchange type. This PR adds

Checklist

• [] I have added unit tests to cover my changes.
• [] I have improved the code quality of this repo. (refactoring, or reduced number of static analyser issues)
• [] I have updated the documentation accordingly

[vorce]

Thanks for the contribution @gordoneliel !

Can you add :headers to@type exchange_kind as well please?

[gordoneliel]

@vorce Added the headers spec and a test for the headers exchange type! Let me know if you need any more changes,thanks.

[gordoneliel]

@vorce Dont mean to pressure, but any chance you can take a peek at this? Happy to make any more changes 😁

[vorce]

@gordoneliel yo, thanks for the patience and apologies for the terrible turn around time. I think the PR looks good!

Looks like we have to fix the CI setup (again) though.

@mkorszun Hey, please have a look at the MR, I think it's ready to merge. I want to take a look at the CI setup and maybe chuck a PR for that, but if someone else gets to it before me all the better 😬