Add comment to flake.nix

Add a comment to the flake file explaining intention and current
limitations of this flake file.

flake.nix

@@ -1,5 +1,16 @@
+# NOTE: This flake is only provided as interface to `bitte` and shouldn't be used otherwise
+#
+# - Until https://github.com/input-output-hk/haskell.nix/issues/1132 is resolved the 
+#   outputs generated by this flake will differ from the respective outputs built via
+#   default.nix because the hackage/stackage.nix revisions differ.
+# - The revisions the nixpkgs and haskell-nix flake inputs have to be kept in sync with
+#   the niv versions manually. When haskell.nix is updated in niv things will break.
+# - Occasionally building flake builds will segfault. The workaround for this is to
+#   disable the garbage collector  `GC_DONT_GC=1  nix build .#web-ghc-server
+#
+# In case you are not sure if you should be using this flake, the answer is: No.
 {
-  description = "Flake for Plutus";
+  description = "plutus flake for bitte deployments";
 
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs?rev=7d71001b796340b219d1bfa8552c81995017544a";