info from https://kate-editor.org/2006/02/09/kateconfig-files/
this page has a section "Enable the Feature", but it is obviously wrong
because the option "Search depth for config file" was removed with
https://cgit.kde.org/ktexteditor.git/commit/src/dialogs/opensaveconfigadvwidget.ui?id=d57ff9c32328644b1b06f0296981a29537430202
Which search depths (up-/downwords in a directory tree) is kate using now?