fix readme

webconfig/buttontask.service.d/override.conf.example

@@ -0,0 +1,14 @@
+# Device-specific touch input. Copy to /etc/systemd/system/buttontask.service.d/override.conf
+# and replace event1 with the correct event number for your touchscreen.
+#
+# Find the touchscreen event number:
+#   grep -l -E 'ABS_X|ABS_MT_POSITION' /sys/class/input/event*/device/capabilities/abs 2>/dev/null \
+#     | sed 's|.*/input/event||;s|/device.*||'
+#
+#   sudo mkdir -p /etc/systemd/system/buttontask.service.d
+#   sudo cp .../override.conf.example /etc/systemd/system/buttontask.service.d/override.conf
+#   sudo systemctl daemon-reload && sudo systemctl restart buttontask
+
+[Service]
+Environment=QT_QPA_GENERIC_PLUGINS=evdevtouch:/dev/input/event1
+Environment=QT_QPA_EVDEV_TOUCHSCREEN_PARAMETERS=/dev/input/event1