snakefmt: add issue link for hatch workaround

Author: branchvincent

Formula/s/snakefmt.rb

@@ -46,7 +46,8 @@ class Snakefmt < Formula
   end
 
   def install
-    # The source doesn't have a valid SOURCE_DATE_EPOCH, so here we set default.
+    # hatch does not support a SOURCE_DATE_EPOCH before 1980.
+    # Remove after https://github.com/pypa/hatch/pull/1999 is released.
     ENV["SOURCE_DATE_EPOCH"] = "1451574000"
 
     virtualenv_install_with_resources