CSV importer for Platform Toolkit's Achievement Editor does not detect CSV files

Steps to reproduce:

1. Open the attached project
2. In the Achievement Editor window, press the Export button
3. Name the file and export the Saves
4. Press the Import button

Actual results: No CSV files are shown in the File browser

Expected results: CSV files are shown in the File browser, including the file exported in step 2

Reproducible with versions: 1.0.0, 1.0.1 (6000.3.11f1, 6000.4.0b12, 6000.5.0a9, 6000.6.0a1)

Can’t test with versions: 6000.0.70f1 (Package is not supported)

Reproducible on (OS): Ubuntu 22

Not reproducible on (OS): macOS 26.3.1