keypad: Set some default row and column spacing

This ensures the keypad will look decent by default.

Fixes GNOME/libhandy#76
11 jobs for keypad-spacing-default in 32 minutes and 33 seconds (queued for 1 minute and 24 seconds)
Status Name Job ID Coverage
  Build
passed api-visibility #842348

00:01:04

passed build-debian-clang #842350

00:04:36

passed build-debian-gcc #842349

00:03:49

passed build-fedora-gcc #842351

00:09:44

passed build-flatpak #842352
flatpak

00:03:42

passed build-flatpak-glade #842353
flatpak

00:05:52

 
  Test+Docs
passed build-gtkdoc #842354

00:04:52

passed unit-test #842355

00:03:57

44.2%
 
  Package
passed package-debian-buster #842356

00:11:12

 
  Test Package
passed autopkgtest-debian-buster-package #842357

00:03:50

passed lintian-debian-buster-package #842358

00:00:52