Mod display name with special symbols breaks MacOS packaging

[penev92]

First reported by @MustaphaTR and his D2k mod, an investigation concluded that the MacOS packaging script can break if the PACKAGING_DISPLAY_NAME in mod.config contains a '\'' (the mod was called "MustaphaTR's D2k Mod".
The Windows installer and Linux AppImages build successfully regardless.

The issue seems to be after https://github.com/OpenRA/OpenRAModSDK/blob/master/packaging/macos/buildpackage.sh#L108 and can likely easily be resolved by escaping input strings.