Support Lix 2.92 (#42)

* Support Lix 2.92

nix-serve-ng can now build against lix by passing -f lix to cabal

the flake now also exports the `lix-serve-ng` package for a version that
is built against lix

* add back configureFlags, lost in rebase

README.md

@@ -96,6 +96,12 @@ in
 }
 ```
 
+## Lix compatability
+
+The default `nix-serve-ng` should work on top of lix, but if you want to build
+it against lix for development or to remove the default nix dependency, you can
+pass `-f lix` to cabal or use the `lix-serve-ng` package from the flake.
+
 ## Motivation
 
 Our requirements for this project were: