feat: adding class for multiple ancestry LD calculation

[addramir]

✨ Context

I provided the context on the last meeting.

🛠 What does this PR implement

🙈 Missing

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• Do these changes cover one single feature (one change at a time)?
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[d0choa]

I don't recommend including this in dev at this stage. At a minimum, it requires tests. Even with tests, I'm not sure it has reached the maturity to tell the world: You can start using this. It can live in its branch and be a draft PR if you want to increase awareness of the work happening here.

[addramir]

Ok, sound reasonable. I will convert it back to draft then. Anyway, Im not planning working on this next month. So it will be in this state for a while.