(Feature) Add resourcepack overlays dependent on Mod loaded state

[Motschen]

Vanilla now allows for subfolders that will be loaded conditionally, dependent on the supported pack version.
Puzzle could expand this system to add support mod-is-loaded conditions, which would help resourcepacks with mod compat avoid spamming the block atlas with textures for mods that aren't even present.

Example of the vanilla syntax:

"overlays": {
    "entries": [
      {
        "directory": "multi_axis_rotation",
        "formats": [16, 420],
        "min_format": 16,
        "max_format": 420
      }
    ]
  }

How a mod support syntax could look like:

"mod-overlays": {
    "entries": [
      {
        "directory": "liltater_compat",
        "modid": "liltater", // or "modid": ["liltater", "bigtater"],
        "formats": [16, 420], // pack formats should also be supported, in case of differences between versions
        "min_format": 16,
        "max_format": 420
      }
    ]
  }