add fullscreen mode

src/main.cpp

@@ -47,6 +47,7 @@ static void PrintUsage() {
 	    "  --game-patch <json>                  Validated patch plan to apply before entry.\n");
 	::printf("  --screen-width <num>                 Window width. Default: 1280.\n");
 	::printf("  --screen-height <num>                Window height. Default: 720.\n");
+	::printf("  --fullscreen                         Run in borderless desktop fullscreen.\n");
 	::printf("  --vblank-frequency <num>             Virtual vblank frequency. Default: 60.\n");
 	::printf("  --console-language <0-29>            Console language. Default: 1 (English US).\n");
 	::printf("  --vulkan-validation <true|false>     Enable Vulkan validation.\n");
@@ -131,6 +132,11 @@ static bool ParseArgs(int argc, char* argv[], RunOptions& options, bool& show_he
 			continue;
 		}
 
+		if (arg == "--fullscreen") {
+			options.config.fullscreen_enabled = true;
+			continue;
+		}
+
 		if (!Common::StartsWith(arg, "--")) {
 			::printf("game input must be provided with --game\n");
 			return false;