CI: .travis.yml: add description for executableNamesToShellComplete

M  .travis.yml

.travis.yml

@@ -73,6 +73,7 @@ env:
     #   command: name of an executable
     #       pkg: Haskell package that builds the executables
     - generateOptparseApplicativeCompletions='false'
+    # [ "binary1" "binary2" ] - should pass " quotes into Nix interpreter
     - executableNamesToShellComplete='[ "hnix" ]'
     # NOTE: Don't fail at configure time if there are multiple versions of the same package in the (recursive) dependencies of the package being built. Will delay failures, if any, to compile time.
     - allowInconsistentDependencies='false'