Adding xkbcommon as a BuildRequires

While doing the kf6 version of this package, I found that xkbcommon is a recommended package to build it. It works without it, but this showed:

-- The following OPTIONAL packages have not been found:
 * XKB (required version >= 0.5.0), XKB API common to servers and clients., <http://xkbcommon.org>

kf5-kwidgetsaddons.spec

@@ -18,6 +18,7 @@ BuildRequires:  kf5-rpm-macros
 BuildRequires:  qt5-qtbase-devel
 BuildRequires:  qt5-qttools-devel
 BuildRequires:  qt5-qttools-static
+BuildRequires:  pkgconfig(xkbcommon)
 
 Requires:       kf5-filesystem >= %{majmin}