core/steam: add kscreen

Signed-off-by: Christian Stewart <christian@aperture.us>

Author: paralin

configs/core/steam/buildroot_ext/package/skiff-core-steam/coreenv/Dockerfile

@@ -26,6 +26,7 @@ RUN \
     usbutils \
     qt5-tools \
     maliit-keyboard \
+    kscreen \
     wget \
     x11vnc \
   && rm -rf /var/cache/*