Add .hlint.yaml

We do want to ignore some hints.

Currently this is:

  - Evaluate: Some type level magic sometimes requires us to write
    expressions that could be evaluated further, but should not.

Related: https://github.com/xmonad/xmonad-contrib/issues/537

.hlint.yaml

@@ -0,0 +1,2 @@
+# Ignore these warnings.
+- ignore: {name: "Evaluate"}