identify_overlaps
identify the overlapping SNPs in the sequences
identify_overlaps(position_reference, genome_position, prev, after)
the mapping of position in SNP matrix to reference genome
the position of the SNP in the reference genome
number of bases before the SNP included in the search string
number of bases after the SNP included in the search string
a list containing 2 dataframes listing the bystander SNPs in the flanking sequence before and after the SNPs