Explain sharp deps and use them in the dev shell

The sharp dependencies are *also* required in the dev shell when
upstream pulls their prebuilt binaries.

flake.nix

@@ -42,7 +42,8 @@
 
           devShell = prev.mkShell {
             buildInputs = with prev;
-              with nodePackages; [
+              with nodePackages;
+              [
                 nodejs
                 node2nix
 
@@ -50,7 +51,7 @@
                 prettier
                 typescript
                 typescript-language-server
-              ];
+              ] ++ packages.nodeEnv.shell.buildInputs;
           };
         };
       };

nix/override.nix

@@ -6,9 +6,14 @@ in nodePackages // {
   shell = nodePackages.shell.override {
     buildInputs = with pkgs; [
       pkgs.nodePackages.node-gyp-build
+      pkgconfig
+
+      # For sharp (dependency of the auto-favicon
+      # generator). This depends on the vips (which uses
+      # gobjects), and builds using node-gyp, which in turn
+      # needs python.
       vips
       glib
-      pkgconfig
     ];
 
     npmFlags = "--ignore-scripts";