Add a little documentation

byg/src/Byg/DependencyRunner.hs

@@ -1,4 +1,11 @@
 {-# LANGUAGE MonoLocalBinds #-}
+
+-- | Run the actual operations from the generated dependencies from DependencyGenerator.
+--
+-- This does not work fully as intended right now (computes more than strictly
+-- needed) and needs to be rewritten in a more testable way. The idea is to only
+-- evaluate something if a future operation depends on it, which is reflected in
+-- the ValueExistence type.
 module Byg.DependencyRunner
   ( DepRunM
   , runDeps