GNOME 45 Port

[nlogozzo]

Closes #401

Folder Open, No Files Found:

Folder Open, With Files, No Selection:

Folder Open, With Files, Selection:

Folder Open, With Files, Selection, Sidebar Collapsed:

[nlogozzo]

@DaPigGuy I think I did the new widgets right on MainWindow 😅

[DaPigGuy]

Just one nit

[DaPigGuy]

The sidebar doesn't seem to collapse properly on shrinking the window due to a missing minimum width (width-request)

[nlogozzo]

The sidebar doesn't seem to collapse properly on shrinking the window due to a missing minimum width (width-request)

The sidebar has:

sidebar: Gtk.Box {
              width-request: 400;

[nlogozzo]

@DaPigGuy I realized what I was doing wrong...fixed in latest commit