[feature] enable loading maps from PK3 archives

[elf-alchemist]

Another limitation I've when using PK3 for a resource archive, is the lack of map-loading from within, and the problem that the maps' multiple lumps being in name-conflict with each other.

On the following autoload PK3, an example of how this can be handled is shown on the mm2.wad/ directory:
https://drive.proton.me/urls/XB8VR8C9HC#sXtJgLIIBFXX

More specifically, this request is to add the set of ns_maps, M_START, M_END, maps/ to the subdirs system.

This would mean reading the contents of that namespace as a set of PWADs following the normal map marker naming convention, and it should only read the PWAD's internal map, if it matches the name of the PWAD itself.

Something akin to maps/MAP26.wad:MAP26, but not maps/MAP26.wad:MAP01.

Or in the case of a possible WAD-within-WAD scenario, these would be explicitly formed by using the namespace markers, M_START and M_END, and have the PWADs in between. If such a scenario is considered.

From a map-making and project leadership perspective, this can be a minor but rather helpful point when handling map submissions that are originally separate from the base resource, which usually only contain the single map itself, in it's given slot.

(P.S. At this point there's a lot going on with this PK3 format, it may just warrant a proper spec to define all of this behavior, to be honest.)

[rfomin]

More specifically, this request is to add the set of ns_maps, M_START, M_END, maps/ to the subdirs system.

We don't need new namespace or WAD markers, just maps/ subdirectory, e.g. maps/MAP01/.

At this point there's a lot going on with this PK3 format, it may just warrant a proper spec to define all of this behavior, to be honest.

The plan is to make it close to ZDoom format: https://zdoom.org/wiki/Using_ZIPs_as_WAD_replacement

[elf-alchemist]

We don't need new namespace or WAD markers, just maps/ subdirectory, e.g. maps/MAP01/.

That works, as well.

The plan is to make it close to ZDoom format: https://zdoom.org/wiki/Using_ZIPs_as_WAD_replacement

Truly, I did derive this suggestion from - how ZDoom handles MAP.wad style lumps inside ZIPs. If a new WAD namespace isn't strictly needed that's fine too.