[mate] switch to kvantum-matcha-dark theme

overlays/mate/etc/environment

+#
+# This file is parsed by pam_env module
+#
+# Syntax: simple "KEY=VAL" pairs on separate lines
+#
+QT_QPA_PLATFORMTHEME=qt5ct

overlays/mate/etc/skel/.config/Kvantum/kvantum.kvconfig

+[General]
+theme=Matcha-Dark

overlays/mate/etc/skel/.config/qt5ct/qt5ct.conf

+[Appearance]
+color_scheme_path=
+custom_palette=false
+icon_theme=Papirus-Dark-Maia
+style=kvantum
+
+[Fonts]
+fixed=@Variant(\0\0\0@\0\0\0\x12\0\x43\0\x61\0n\0t\0\x61\0r\0\x65\0l\0l@$\0\0\0\0\0\0\xff\xff\xff\xff\x5\x1\0\x32\x10)
+general=@Variant(\0\0\0@\0\0\0\x12\0\x43\0\x61\0n\0t\0\x61\0r\0\x65\0l\0l@$\0\0\0\0\0\0\xff\xff\xff\xff\x5\x1\0\x32\x10)
+
+[Interface]
+activate_item_on_single_click=1
+buttonbox_layout=0
+cursor_flash_time=1000
+dialog_buttons_have_icons=1
+double_click_interval=400
+gui_effects=@Invalid()
+menus_have_icons=true
+stylesheets=@Invalid()
+
+[SettingsWindow]
+geometry=@ByteArray(\x1\xd9\xd0\xcb\0\x2\0\0\0\0\x1\x9a\0\0\x1\x1\0\0\x3\xd8\0\0\x3w\0\0\x1\x9b\0\0\x1\x19\0\0\x3\xd7\0\0\x3v\0\0\0\0\0\0\0\0\x5\0)