drs: rgb camera hook (#524)

## Link to GitHub Issue, if one exists
n/a

## Description of change
Add plug&play hooks for RGB camera in DRS.

## Testing
Seems to work with my crappy Logitech C270

Camera options (brightness etc) seem to work in test menu as well).

Tested by another user with realsense camera + logitech camera, both
cams were detected correctly.

src/spice2x/games/drs/drs.cpp

@@ -8,6 +8,7 @@
 #include "util/detour.h"
 #include "util/logging.h"
 #include "util/memutils.h"
+#include "rgb_cam.h"
 
 #pragma pack(push)
 
@@ -150,6 +151,7 @@ namespace games::drs {
     char DRS_TAPELED[DRS_TAPELED_COLS_TOTAL][3] {};
     bool DISABLE_TOUCH = false;
     bool TRANSPOSE_TOUCH = false;
+    bool RGB_CAMERA_HOOK = false;
 
     std::vector<TouchEvent> TOUCH_EVENTS;
 
@@ -313,6 +315,10 @@ namespace games::drs {
         } else {
             log_info("drs", "no native input method detected");
         }
+
+        if (RGB_CAMERA_HOOK) {
+            init_rgb_camera_hook();
+        }
     }
 
     void DRSGame::detach() {