feat: add a prioritised item buffer

[EdanToledo]

What?

Add prioritised item buffer.

Why?

Its useful to have a simple buffer type such as the item buffer in a prioritised variant.

How?

Wrap the prioritised trajectory buffer in the same way we wrap the trajectory buffer in the item buffer case.

[LabChameleon]

Is there any news on this PR? Do you know if it is safe to use?

[JesseFarebro]

I was also looking specifically for this, would be nice to have this PR merged 🙏

[callumtilbury]

Hi @LabChameleon & @JesseFarebro 👋🏻 Sorry for the delay! A few other projects had top priority for some time, but we're back now & we will be getting this merged ASAP :)

[callumtilbury]

Need to merge in #27, but otherwise LGTM 🥇

(Apologies for delay!)