Added NUR overlay

overlays/default.nix

@@ -1,3 +1,5 @@
+{ inputs, ... }:
 [
-  (import ./discord.nix)
+  (import ./discord.nix { })
+  (import ./nur.nix { nur = inputs.nur; })
 ]

overlays/discord.nix

@@ -1,6 +1,9 @@
-self: super:
-{
-  discord = super.discord.overrideAttrs (_: {
-    src = builtins.fetchTarball https://discord.com/api/download?platform=linux&format=tar.gz;
-  });
-}
+{ ... }:
+(
+  final: prev:
+  {
+    discord = prev.discord.overrideAttrs (_: {
+      src = builtins.fetchTarball https://discord.com/api/download?platform=linux&format=tar.gz;
+    });
+  }
+)

overlays/nur.nix

@@ -0,0 +1,9 @@
+{ nur, ... }:
+(
+  final: prev: {
+    nur = import nur {
+      nurpkgs = prev;
+      pkgs = prev;
+    };
+  }
+)