lib: get rid of the redundant let-in block

lib/stdlib-extended.nix

@@ -1,18 +1,21 @@
-# Cconvenience function that returns the given Nixpkgs standard library
+# Convenience function that returns the given Nixpkgs standard library
 # extended with our functions using `lib.extend`.
-nixpkgsLib: inputs: let
-  mkNvimLib = import ./.;
-in
+nixpkgsLib: inputs:
+nixpkgsLib.extend (self: super: {
   # WARNING: New functions should not be added here, but to files
   # imported by `./default.nix` under their own categories. If your
   # function does not fit to any of the existing categories, create
   # a new file and import it in `./default.nix.`
-  nixpkgsLib.extend (self: super: {
-    nvim = mkNvimLib {
-      inherit inputs;
-      lib = self;
-    };
 
-    # For forward compatibility.
-    literalExpression = super.literalExpression or super.literalExample;
-  })
+  # Makes our custom functions available under `lib.nvim` where stdlib-extended.nix is imported
+  # with the appropriate arguments. For end-users, a `lib` output will be accessible from the flake.
+  # E.g. for an input called `neovim-flake`, `inputs.neovim-flake.lib.nvim` will return the set
+  # below.
+  nvim = import ./. {
+    inherit inputs;
+    lib = self;
+  };
+
+  # For forward compatibility.
+  literalExpression = super.literalExpression or super.literalExample;
+})