[ENH]: Support "xi" correlation metric for functional connectivity

[synchon]

Are you requiring a new dataset or marker?

• I understand this is not a marker or dataset request

Which feature do you want to include?

Adapt https://github.com/czbiohub-sf/xicor to be used as a correlation metric for functional connectivity markers.

How do you imagine this integrated in junifer?

As an option for nilearn's ConnectivityMeasure.

Do you have a sample code that implements this outside of junifer?

https://github.com/czbiohub-sf/xicor

Anything else to say?

No response