Implementing support for suborg level rulesets

## New Feature

We're investigating implementing support for rulesets in suborgs.

It seems that, with this missing piece, rulesets can completely replace branch protections (and their limitations such as [the api not supporting branch name patterns](https://github.com/github/safe-settings/issues/562))

It would be good to get some more detail on [this comment](https://github.com/github/safe-settings/pull/519) @decyjphr

> (deferring the handling of rulesets entries in .yml until ruleset targeting using repo properties is available and we would want to do the same in suborg yml)

I note that `repository_property` is recently available in [org ruleset conditions](https://docs.github.com/en/rest/orgs/rules?apiVersion=2022-11-28#create-an-organization-repository-ruleset) but am wondering how this might affect the implementation of suborg rulesets?

Wouldn't suborg rulesets be implemented as repo rulesets in the same way as eg: branch protections?

It would be great if you could give a sketch of the requirements here or indicate if this is on the immediate roadmap, thanks