ibus-engines.typing-booster: init at 2.1.1

This package providesa completion input method for faster typing.
See https://mike-fabian.github.io/ibus-typing-booster

Detailed instructions how to activate this IBus engine on your desktop
can be found in the upstream docs: https://mike-fabian.github.io/ibus-typing-booster/documentation.html

A simple VM with the Gnome3 desktop and activated `ibus' looks like
this:

```nix
{
  emojipicker = { pkgs, ... }: {
    services.xserver = {
      enable = true;
      desktopManager.gnome3.enable = true;
      desktopManager.xterm.enable = false;
    };
    users.extraUsers.vm = {
      password = "vm";
      isNormalUser = true;
    };
    i18n.inputMethod.ibus.engines = [
      pkgs.ibus-engines.typing-booster
    ];
    i18n.inputMethod.enabled = "ibus";
    virtualisation.memorySize = 2048;
  };
}
```

Fixes #38721

pkgs/tools/inputmethods/ibus-engines/ibus-typing-booster/wrapper.nix

@@ -0,0 +1,30 @@
+{ typing-booster, symlinkJoin, hunspellDicts, lib, makeWrapper
+, langs ? [ "de-de" "en-us" "es-es" "it-it" "sv-se" "sv-fi" ]
+}:
+
+let
+
+  hunspellDirs = with lib; makeSearchPath ":" (flatten (flip map langs (lang: [
+    "${hunspellDicts.${lang}}/share/hunspell"
+    "${hunspellDicts.${lang}}/share/myspell"
+    "${hunspellDicts.${lang}}/share/myspell/dicts"
+  ])));
+
+in
+
+symlinkJoin {
+  name = "${typing-booster.name}-with-hunspell";
+  paths = [ typing-booster ];
+  nativeBuildInputs = [ makeWrapper ];
+
+  postBuild = ''
+    for i in bin/emoji-picker libexec/ibus-{setup,engine}-typing-booster; do
+      wrapProgram "$out/$i" \
+        --prefix NIX_HUNSPELL_DIRS : ${hunspellDirs}
+    done
+
+    sed -i -e "s,${typing-booster},$out," $out/share/ibus/component/typing-booster.xml
+  '';
+
+  inherit (typing-booster) meta;
+}