translations: add German translation (#6601)

This PR adds a translation for German `de_DE`.

Additionally it excludes all `*.po` files from the typos CI action.

Some comments on the decisions I made (open to discuss them):

- I choosed to use `du` instead of `Sie` as this seems appropriate
  to me.
- I added `Window` (`Fenster` in German) to all split commands
  as it appears more naturally to me.

src/os/i18n.zig

@@ -24,6 +24,7 @@ const log = std.log.scoped(.i18n);
 ///   3. Most preferred locale for a language without a country code.
 ///
 pub const locales = [_][:0]const u8{
+    "de_DE.UTF-8",
     "zh_CN.UTF-8",
 };