ci(flake): add flake description

Signed-off-by: Christina Sørensen <christina@cafkafk.com>

flake.nix

@@ -1,4 +1,6 @@
 {
+  description = "The EZA flake for developing and releasing (soon)";
+
   inputs = {
     flake-utils.url = "github:numtide/flake-utils";
     naersk.url = "github:nix-community/naersk";