biology/peak-classifier: Classify peaks based on GFF features

Classify ChIP/ATAC-Seq peaks based on features provided in a GFF

Peaks are provided in a BED file sorted by chromosome and position.
The GFF must be sorted by chromosome and position, with gene-level
features separated by ### tags and each gene organized into
subfeatures such as transcripts and exons. This is the default for
common data sources.