Add `generate_macro_yaml` macro

### Describe the feature
Generate boilerplate yaml for macro documentation as described [here](https://docs.getdbt.com/reference/macro-properties)

### Describe alternatives you've considered
Building yaml by hand

### Additional context
It wouldn't do anything fancy, but it could be helpful for 1) consistency across developers and 2) publicizing that macros can also be documented in yaml

### Who will this benefit?
Developers of macros looking to generate consistent yaml for documentation

### Are you interested in contributing this feature?

Yes (: