added mb_string extension as a requirement
added mb_string extension as a requirement

Teino1978-Corp/Teino1978-Corp-csv,stof/csv,thephpleague/csv,vlakarados/csv,hmcclungiii/csv-1,postalservice14/csv,mortenhauberg/csv,Perlkonig/grav-plugin-table-importer,HeyRatFans/csv