Assembly3 STEP inport under FreeCAD 0.21 has issues with extension case sensitivity

[ToniTen]

Under Link Daily, Assembly3 step file import (asm3CmdImport) does not care about the case sensitivity of the extension on the files it imports However, under 0.21, it does care, and will only show .step files and not .STEP files, unless you disable the filtering so it can show all files Regular FreeCAD import (file/Import) works properly, and uses the same open file dialog as Link Daily.

Obviously the open file dialogs are completely different, which I assume is the root source of the problem. I guess that Link Daily uses the built in Qt file picker while 0.21 uses the system's GTK3 one, that is known for being more picky about such things. This is a problem when interacting with other people, since people from Windows do not usually care about case sensitivity in file names. Files exported from FreeCAD have the step extension in lower case so it's not usually a problem.

Freecad versions used: Link Daily

OS: Ubuntu Core 20 (XFCE/xubuntu)
Word size of FreeCAD: 64-bit
Version: 2023.321.14555 (Git shallow)
Build type: Release
Branch: (HEAD detached at 2023.03.21-edge)
Hash: 2a426c127ac4e741b11bae3d82839ee435608e1f
Python version: 3.8.10
Qt version: 5.15.7
Coin version: 4.0.1
OCC version: 7.6.3
Locale: English/United States (en_US)

0.21

OS: Ubuntu Core 20 (XFCE/xubuntu)
Word size of FreeCAD: 64-bit
Version: 0.21.0.33234 (Git) Snap 709
Build type: Release
Branch: master
Hash: 1c370eff57a048f22d226843a21cf7cfbc585870
Python 3.8.10, Qt 5.15.7, Coin 4.0.0, Vtk 7.1.1, OCC 7.6.3
Locale: English/United States (en_US)
Installed mods: 
  * fasteners 0.4.56
  * Assembly3 0.12.0
  * lattice2 1.0.0
  * Manipulator 1.5.0