Fix aspell on Linux (and probably Mac, too)

nix/modules/emacs.nix

@@ -3,6 +3,7 @@ with config.lib.file;
 let dotdir = "${config.home.homeDirectory}/.dotfiles";
     isOnMac = pkgs.stdenv.hostPlatform.isDarwin;
     emacsWithPackages = (pkgs.emacsPackagesFor pkgs.emacs29).emacsWithPackages;
+    aspell = (pkgs.aspellWithDicts (d: [d.en]));
 in
 {
   home.packages = with pkgs; let
@@ -12,7 +13,7 @@ in
       ]))
       zstd
       emacs-lsp-booster
-      (aspellWithDicts (d: [d.en]))
+      aspell
     ];
     macPackages = basePackages ++ [ coreutils ];
   in
@@ -21,4 +22,12 @@ in
   xdg.configFile = {
     "emacs".source = mkOutOfStoreSymlink "${dotdir}/thoom-emacs";
   };
+
+  # The aspell wrapper created by aspellWithDicts only wraps the
+  # binary, not the library, so we need to write a config file that
+  # tells it where to find things for libenchant to work. See:
+  # https://discourse.nixos.org/t/aspell-dictionaries-are-not-available-to-enchant/39254
+  home.file.".aspell.conf".text = ''
+dict-dir ${aspell}/lib/aspell
+'';
 }