add link back to GitHub repo

docs/source/index.rst

@@ -6,6 +6,8 @@
 Welcome to STRling's documentation!
 ===================================
 
+STRling code: https://github.com/quinlan-lab/STRling
+
 STRling (pronounced like “sterling”) is a method to detect large STR expansions from short-read sequencing data. It is capable of detecting novel STR expansions, that is expansions where there is no STR in the reference genome at that position (or a different repeat unit from what is in the reference). It can also detect STR expansions that are annotated in the reference genome. STRling uses kmer counting to recover mis-mapped STR reads. It then uses soft-clipped reads to precisely discover the position of the STR expansion in the reference genome.
 
 .. toctree::