Allow extra chromosomes in map files

[bunop]

Is your feature request related to a problem? Please describe.
detectRUNS should be able to deal with extra chromosomes (Like Scaffold_12345 or Contig_1234)

Describe the solution you'd like
Functions need to be implemented (and tested) to work with str chromosomes, which can be also a custom string.

Describe alternatives you've considered
A workaround could be to replace the chromosome names with numbers, and then re-apply the original names on the returned dataframe. However, functions like Froh_inbreeding could have issues when a lot of chromosomes (>100) are present in the same moment

Additional context
issue #23 is related to this problem