Sort language source files by name for consistent mapLocales order

[akwls]

I'm using easy_localization:generate in my company's Flutter app.

Recently, I added some code to our GitHub workflow to check if developers have run the easy_localization:generate command after adding or editing localization strings.

The workflow runs:

dart run easy_localization:generate -S assets/translations
dart run easy_localization:generate -S assets/translations -f keys -o locale_keys.g.dart

After that, the workflow fails if there are any code changes.

The problem is that codegen_loader.g.dart differs from the base code when the workflow is executed. The reason for this failure is that the order of the mapLocales variable in codegen_loader.g.dart is inconsistent.

For example:

Base code: {"en": en, "ko": ko}
GitHub workflow result: {"ko": ko, "en": en}

I believe this happens because, when the asset file list is retrieved from the directory, the order of files is not guaranteed. Therefore, I suggest sorting the file list based on the file names to ensure consistency