The lack of XCURSOR_THEME not being set means applications who wish to manipulate the cursor like wezterm, can't properly do so because they don't know the theme, and the default theme is missing.

The lack of this default theme also results in a missing cursor in the wayland SDDM screen under the kwin_wayland

Adding /usr/share/icons/default/index.theme
with the content
```
[Icon Theme]
Inherits=breeze_cursors
```

Fixes both issues, though  XCURSOR_THEME should probably be set somewhere