engine: host: expose new -borderless flag in command line help

engine/common/host.c

@@ -115,6 +115,7 @@ void Sys_PrintUsage( void )
 	O("-oldfont         ", "enable unused Quake font in Half-Life")
 	O("-width <n>       ", "set window width")
 	O("-height <n>      ", "set window height")
+	O("-borderless      ", "run engine in fullscreen borderless mode")
 	O("-fullscreen      ", "run engine in fullscreen mode")
 	O("-windowed        ", "run engine in windowed mode")
 	O("-ref <name>      ", "use selected renderer dll")