vscode-extensions: recurse into publishers

The vscode-extensions set is already marked as recurseIntoAttrs, but
this has no effect, since this set is two layers deep instead of the
usual one which recurseIntoAttrs applies to.

By applying recurseIntoAttrs to all publishers, the extensions will be
considered by nix tools when listing packages.

pkgs/misc/vscode-extensions/default.nix

@@ -10,6 +10,7 @@ in
 # So an extension's attribute name should be of the form:
 # "${mktplcRef.publisher}.${mktplcRef.name}".
 #
+stdenv.lib.mapAttrs (_n: stdenv.lib.recurseIntoAttrs)
 {
 
   alanz.vscode-hie-server = buildVscodeMarketplaceExtension {