minor request to update readme

[devonorourke]

Hi,
Thank you for maintaining this software. In my first attempt at running the program I received an error when trying to use a .vcf file. After searching through the issues posts I came across this thread which resolved my problem: if invoking the -T parameter to read from the GT field of the .vcf file, you also need to invoke the -c parameter.
Perhaps I'm mistaken with these parameters, but if this is in fact true, it would be helpful to make a minor update to the readme/documentation when using vcf files to remind users to use those flags (if needed). Maybe something like this?:

./ngsrelate  -h my.VCF.gz -O vcf.res
./ngsrelate  -h my.VCF.gz -O vcf.res -T GT -c    ## if specifying values from GT field in .vcf

Cheers,
Devon

[KHanghoj]

Thanks for the comment. I have added this to the readme.