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

doc/package-notes.xml

@@ -814,4 +814,64 @@ citrix_receiver.override {
    </para>
   </section>
  </section>
+ <section xml:id="sec-ibus-typing-booster">
+  <title>ibus-engines.typing-booster</title>
+
+  <para>This package is an ibus-based completion method to speed up typing.</para>
+
+  <section xml:id="sec-ibus-typing-booster-activate">
+   <title>Activating the engine</title>
+
+   <para>
+    IBus needs to be configured accordingly to activate <literal>typing-booster</literal>. The configuration
+    depends on the desktop manager in use. For detailed instructions, please refer to the
+    <link xlink:href="https://mike-fabian.github.io/ibus-typing-booster/documentation.html">upstream docs</link>.
+   </para>
+   <para>
+    On NixOS you need to explicitly enable <literal>ibus</literal> with given engines
+    before customizing your desktop to use <literal>typing-booster</literal>. This can be achieved
+    using the <literal>ibus</literal> module:
+<programlisting>{ pkgs, ... }: {
+  i18n.inputMethod = {
+    enabled = "ibus";
+    ibus.engines = with pkgs.ibus-engines; [ typing-booster ];
+  };
+}</programlisting>
+   </para>
+  </section>
+
+  <section xml:id="sec-ibus-typing-booster-customize-hunspell">
+   <title>Using custom hunspell dictionaries</title>
+
+   <para>
+    The IBus engine is based on <literal>hunspell</literal> to support completion in many languages.
+    By default the dictionaries <literal>de-de</literal>, <literal>en-us</literal>, <literal>es-es</literal>,
+    <literal>it-it</literal>, <literal>sv-se</literal> and <literal>sv-fi</literal>
+    are in use. To add another dictionary, the package can be overridden like this:
+<programlisting>ibus-engines.typing-booster.override {
+  langs = [ "de-at" "en-gb" ];
+}</programlisting>
+   </para>
+   <para>
+     <emphasis>Note: each language passed to <literal>langs</literal> must be an attribute name in
+     <literal>pkgs.hunspellDicts</literal>.</emphasis>
+   </para>
+  </section>
+
+  <section xml:id="sec-ibus-typing-booster-emoji-picker">
+   <title>Built-in emoji picker</title>
+
+   <para>
+    The <literal>ibus-engines.typing-booster</literal> package contains a program
+    named <literal>emoji-picker</literal>. To display all emojis correctly,
+    a special font such as <literal>noto-fonts-emoji</literal> is needed:
+   </para>
+   <para>
+    On NixOS it can be installed using the following expression:
+<programlisting>{ pkgs, ... }: {
+  fonts.fonts = with pkgs; [ noto-fonts-emoji ];
+}</programlisting>
+   </para>
+  </section>
+ </section>
 </chapter>