leaflet: Init the style class for the default fold

Add the 'unfolded' style class by default to match the default fold
value.

Fixes Librem5/libhandy#198.
11 jobs for leaflet-default-style-class in 17 minutes and 20 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #246902
librem5
api-visibility

00:02:18

passed #246904
librem5
build-debian-clang

00:03:25

passed #246903
librem5
build-debian-gcc

00:02:32

passed #246905
librem5
build-fedora-gcc

00:03:04

 
  Test+Docs
passed #246906
librem5
build-gtkdoc

00:02:25

passed #246907
librem5
unit-test

00:02:23

43.2%
 
  Package
passed #246908
librem5
package-debian-buster

00:02:26

passed #246909
librem5:arm64
package-debian-buster:arm64

00:06:37

failed #246910
flatpak allowed to fail
package-flatpak

00:00:46

 
  Test Package
passed #246911
librem5
autopkgtest-debian-buster-package

00:02:31

passed #246912
librem5
lintian-debian-buster-package

00:00:58

 
Name Stage Failure
failed
package-flatpak Package
Committing stage finish to cache
Exporting sm.puri.Handy.Demo to repo
error: Writing content object: min-free-space-percent '3%' would be exceeded, at least 4.1?kB requested
Export failed: Child process exited with code 1
Uploading artifacts...
_build/meson-logs/meson-log.txt: found 1 matching files
WARNING: sm.puri.Handy.Demo-dev.flatpak: no matching files
Uploading artifacts to coordinator... ok
id=246910 responseStatus=201 Created token=ReaKbywb
ERROR: Job failed: exit code 1