Add option for more than one chromosome

## Goal
Enable the user to input data for multiple chromosomes.
Relate to the issue https://github.com/AlphaGenes/AlphaPeel/issues/101

## Proposed approach
A draft plan: 
- Add a chrom-map file for the user to map the markers to the chromosome
- Launch a separate peeling session for each chromosome, making thread-level parallelisation possible

## Scope
Unclear

## Done when
Unclear
