Merge "Language list heading: add padding and make it bold"

          style="?android:attr/preferenceCategoryStyle"

          android:layout_width="match_parent"

          android:layout_height="36dp"

          android:paddingStart="12dp"

          android:paddingEnd="12dp"

          android:gravity="center_vertical"

          android:paddingStart="18dp"

          android:paddingEnd="18dp"

          android:textColor="?android:attr/colorAccent"

          tools:text="@string/language_picker_section_all"/>