FAQ.md: Add an entry for generated headers [skip ci]
FAQ.md: Add an entry for generated headers [skip ci]

Closes https://github.com/mesonbuild/meson/issues/5624

mesonbuild/meson,pexip/meson,QuLogic/meson,jpakkane/meson,jpakkane/meson,becm/meson,pexip/meson,becm/meson,QuLogic/meson,becm/meson,mesonbuild/meson,becm/meson,pexip/meson,QuLogic/meson,jpakkane/meson,QuLogic/meson,mesonbuild/meson,pexip/meson,QuLogic/meson,mesonbuild/meson,mesonbuild/meson,QuLogic/meson,pexip/meson,QuLogic/meson,mesonbuild/meson,becm/meson,QuLogic/meson,pexip/meson,jpakkane/meson,mesonbuild/meson,jpakkane/meson,jpakkane/meson,mesonbuild/meson,pexip/meson,becm/meson,jpakkane/meson,pexip/meson,becm/meson,QuLogic/meson,pexip/meson,mesonbuild/meson,mesonbuild/meson,becm/meson,jpakkane/meson,becm/meson,pexip/meson,becm/meson,jpakkane/meson