Add Czech keyboard layouts
Czech Standard (= qwertz)
The accented letters layout corresponds to the UCW  layout shipped with xkb, so we follow this precedent.
Like the DE layout, and unlike the US layout, the CZ layout has a comma key and a narrower space bar. The added comma key also serves as a visual balance to the added accents key, to keep the spacebar centered.
The layouts have been tested manually on PinePhone.