Install a startup script for X11-based sessions

It seems the X11 session is still going to be used for a while on KDE
Neon and Manjaro. Let's at least make sure both X11 and Wayland are
launched the same way

bin/CMakeLists.txt

 configure_file(plasma-bigscreen-wayland.in ${CMAKE_CURRENT_BINARY_DIR}/plasma-bigscreen-wayland)
-install(PROGRAMS ${CMAKE_CURRENT_BINARY_DIR}/plasma-bigscreen-wayland DESTINATION ${BIN_INSTALL_DIR})
+install(PROGRAMS
+	${CMAKE_CURRENT_BINARY_DIR}/plasma-bigscreen-wayland
+	plasma-bigscreen-x11
+	DESTINATION ${BIN_INSTALL_DIR})
 
 configure_file(plasma-bigscreen-wayland.desktop.cmake ${CMAKE_CURRENT_BINARY_DIR}/plasma-bigscreen-wayland.desktop)
+configure_file(plasma-bigscreen-x11.desktop.cmake ${CMAKE_CURRENT_BINARY_DIR}/plasma-bigscreen-x11.desktop)
+
 install(FILES
-        ${CMAKE_CURRENT_BINARY_DIR}/plasma-bigscreen-wayland.desktop
-        DESTINATION ${KDE_INSTALL_DATADIR}/wayland-sessions
+	${CMAKE_CURRENT_BINARY_DIR}/plasma-bigscreen-wayland.desktop
+	${CMAKE_CURRENT_BINARY_DIR}/plasma-bigscreen-x11.desktop
+    DESTINATION ${KDE_INSTALL_DATADIR}/wayland-sessions
 )

bin/plasma-bigscreen-x11

+#!/bin/sh
+
+[ -f /etc/profile ] && . /etc/profile
+
+export QT_QPA_PLATFORMTHEME=KDE
+
+export QT_QUICK_CONTROLS_STYLE=Plasma
+export QT_ENABLE_GLYPH_CACHE_WORKAROUND=1
+export QT_QUICK_CONTROLS_MOBILE=true
+export PLASMA_PLATFORM=mediacenter
+export QT_IM_MODULE=qtvirtualkeyboard
+export QT_VIRTUALKEYBOARD_STYLE=Plasma
+export QT_FILE_SELECTORS=mediacenter
+
+export PLASMA_DEFAULT_SHELL=org.kde.plasma.mycroft.bigscreen
+startplasma-x11

bin/plasma-bigscreen-x11.desktop.cmake

+[Desktop Entry]
+Exec=dbus-run-session ${CMAKE_INSTALL_FULL_BINDIR}/plasma-bigscreen-x11
+TryExec=${CMAKE_INSTALL_FULL_BINDIR}/plasma-bigscreen-x11
+DesktopNames=KDE
+Name=Plasma Bigscreen (X11)
+Comment=Plasma Bigscreen by KDE (X11)
+X-KDE-PluginInfo-Version=${PROJECT_VERSION}