Snap issues

I'm creating a new issue to list all the current issues with the snap packages, since in addition to the two open issues, there are a few other problems.

• https://github.com/neovide/neovide/issues/1081. This one seems to be related to not setting the correct plugs to properly allow GPU access. This can be worked around by adding the --devmode flag. Note that we are still waiting for logs from users to know exactly what's missing

• https://github.com/neovide/neovide/issues/1060. This seems to be caused by a missing libwayland-egl1 library. It can likely also be worked around with the --devmode flag in which case the library would be read from the host. However there's currently no user reports.

• The stage-packages list https://github.com/neovide/neovide/blob/3efc3c1759c80368090e8f747b188b2155ea68f0/snap/snapcraft.yaml#L93-L109 contains a few dev packages. They should be replaced by normal ones

• Neovim is embedded in the snap package, and currently the build fails because it cannot download https://github.com/neovim/deps/raw/master/opt/LuaJIT-2.0.4.tar.gz for some reason. I haven't checked it in detail, but it is possible that it tries to use the wrong git tag of Neovim. I don't think this should be fixed, instead we should add Neovim as a normal dependency, there should be a working snap available in the normal package manager.

Personally I don't have any experience with developing snap packages, so I don't know if I can fix it properly myself, it least not without a bit of studying. I found out all of the above by reading the snapcraft.yml and a little bit of googling. Furthermore I can only really test this inside WSL, and I currently don't use any snaps. But I do have systemd support through https://github.com/nullpo-head/wsl-distrod, and I did test some snap previously, and WSLg is also setup so I can run Neovide normally with that. So in theory I could get snap support working.

Therefore it would be good if someone else could try.