[Enhancement] Support loading mods inside folders to help organize large modpacks

[Asynchro-Dev]

This would make it easier to organize large modpacks into categorized folders (e.g., mods/performance/, mods/optional/, etc).

Currently, Fabric Loader only loads .jar files from the top level mods/ directory. For large modpacks, this can become hard to maintain. Many modpack developers and users would benefit from being able to group mods. Like that:

mods/
├── main/
│   ├── create.jar
│   └── (...)
├── optimization/
│   └── sodium.jar
│   └── (...)
└── visuals/
    └── iris.jar
    └── (...)

Suggested solution

Use Depth-First Search (DFS) to recursively scan the mods/ folder for .jar files, allowing mods to be organized in subfolders. Optionally, include a depth limit to prevent excessive traversal.

Its not that hard to implement, but it would be a great update for modpack creators

[Poopooracoocoo]

#81 was already opened for this suggestion. I like the approach of a JVM argument like #994 implements.