Backport TARGET_APPIMAGE and set fsname and subtype to squashfuse

[probonopd]

Backport TARGET_APPIMAGE and set fsname and subtype to squashfuse

Reference:

• Use "fuse" fstype instead of "fuse.<name-of-the-AppImage>" AppImage/type2-runtime#83

[probonopd]

Set fsname and subtype to "squashfs" - did it do anything? Still getting the same error on FreeBSD...
Or did I do it wrong?

[probonopd]

We still get

$ mount
...
mkappimage-709-x86_64.AppImage on /tmp/.mount_mkappiKbBbOk type fuse.mkappimage-709-x86_64.AppImage (ro,nosuid,nodev,relatime,user_id=1000,group_id=100)

instead of

mkappimage-709-x86_64.AppImage on /tmp/.mount_mkappiKbBbOk type fuse.squashfuse (ro,nosuid,nodev,relatime,user_id=1000,group_id=100)

so

https://github.com/probonopd/static-tools/pull/29/files#diff-1bdc3b5fec7a6822b1bc75067ef43e140288c370d4d6dbab4f699911f9eee8baR819-R820

was wrong.