libtrainsim snap release

Recently I found some time to publish the libtrainsim reference implementation to the snap store.

Because this snap uses the core20 and the gnome-40 extension it will only be stable and available to more architectures than amd64 once version 4.5.5 or 4.6.0 of snapcraft is released which will hopefully happen in the next week.

Also LedController 2.0.0 will be out soon. I added a new example which breaks the CI. Once that is fixed I will release version 2.0.0.