Evolution: provide an appimage workflow

[McArcady]

No description provided.

[McArcady]

• add option and build instructions to generate the appimage package format (x86_64)
• add the corresponding workflow for nightly build
• test on a recent Ubuntu
• test on a recent Debian
• test on a recent Fedora/Redhat
• test on a recent Arch

[McArcady]

The AppImage generation on the github CI fails for the time being because of this problem with linuxdeploy.
But tt's being worked on by the maintainer!

[McArcady]

The AppImage generation workflow is fixed.

[thiras]

It doesn't work on up-to-date Ubuntu 20.04

Here is the logs;

Starting LinuxDwarfPack-0.47.04-r3-x86_64
- configuration and game saves are stored in /home/thiras/.lnp/
- feedback or issues? see http://www.bay12forums.com/smf/index.php?topic=157712
- created with lnp-forge: https://github.com/McArcady/lnp-forge

Creating overlay of /home/thiras/.lnp/ and /tmp/.mount_LinuxDXVA0Oo in /tmp/lnp-I3Gdzc...
/tmp/.mount_LinuxDXVA0Oo/AppRun: 23: unionfs: not found
/tmp/.mount_LinuxDXVA0Oo/AppRun: 26: ./startlnp.sh: not found
fusermount: entry for /tmp/lnp-I3Gdzc not found in /etc/mtab
/tmp/lnp-I3Gdzc unmounted.

[McArcady]

@thiras it looks like you need package unionfs or unionfs-fuse.
I've added some checking in the Appimage startup script to detect this problem.

[McArcady]

For Ubuntu/Debian users, there is a .deb package available here.
Packages for other distros are also available, but not tested yet.

[McArcady]

AppImage has been tested and reported ok on all kind of distros (except RedHat)