Config files inside a folder is not picked up

### :information_source: Info
Version: `e.g. v0.9.2`

### :speech_balloon: Description
I created 3 `flutter_launcher_icons-.yaml` files and put them inside a folder in the project root. When I run the command `fvm flutter pub run flutter_launcher_icons:main -f config/generate_appicons/flutter_launcher_icons*`, it's not generating the icons.

But if I place those files in the project root itself and run `fvm flutter pub run flutter_launcher_icons:main -f flutter_launcher_icons*`, it works.

Not sure if this is my design or not. But I'd like to keep these config files in a separate folder to keep the project structure organised. But this issue is preventing that.

Start at the `flutter_launcher_icons:main` entry point and reproduce the command using `config/generate_appicons/flutter_launcher_icons*`. Compare it with the working root-level `flutter_launcher_icons*` command, then verify that configuration files in the nested folder are discovered and generate the expected icons.

Written by the indexing model from the issue text.