overrides.nix: Move into overrides/default.nix

I will implement some automation around creating these which will have supplementary files that shouldn't pollute the project root.

README.md

@@ -192,7 +192,7 @@ poetry2nix.mkPoetryEditablePackage {
 
 ### defaultPoetryOverrides
 
-_poetry2nix_ bundles a set of default overrides that fix problems with various Python packages. These overrides are implemented in [overrides.nix](./overrides.nix).
+_poetry2nix_ bundles a set of default overrides that fix problems with various Python packages. These overrides are implemented in [overrides](./overrides/default.nix).
 
 ### overrides.withDefaults
 Returns a list containing the specified overlay and `defaultPoetryOverrides`.

default.nix

@@ -437,7 +437,7 @@ lib.makeScope pkgs.newScope (self: {
 
     Can be overriden by calling defaultPoetryOverrides.overrideOverlay which takes an overlay function
   */
-  defaultPoetryOverrides = self.mkDefaultPoetryOverrides (import ./overrides.nix { inherit pkgs lib; });
+  defaultPoetryOverrides = self.mkDefaultPoetryOverrides (import ./overrides { inherit pkgs lib; });
 
   /*
     Convenience functions for specifying overlays with or without the poerty2nix default overrides