`Catch._observation` does not follow the other environments with `_get_observation`

I didn't find a parent common interface for all the `bsuite` environments, but a common patter is to have a method `get_observation` to collect the current observation.

`Catch`, however, is the only environment to have an `_observation` method in place of a `_get_observation` one.
https://github.com/deepmind/bsuite/blob/6d8f64997ca256473c3d10be021431facc5a14d7/bsuite/environments/catch.py#L109-L114

Is there any specific reason why?
If not, would it be reasonable to omogenise the interface and make `Catch` compliant?

Contex:
I usually use a simple interface to interoperate between `gym`, `bsuite`, `dm_env` and other common libraries, and the lack of a shared interface for `bsuite.Environment`s is an obstacle.

See also #44 for a tentative edit of `Catch`.
It does note modify the parent `Environment` yet.

Thanks,
Edu