camera: add PipeWire camera support

The PipeWire camera will enumerate the pipewire Video/Source nodes with
their formats.

When capturing is started, a stream to the node will be created and
frames will be captured.

src/camera/SDL_camera.c

@@ -34,6 +34,9 @@ static const CameraBootStrap *const bootstrap[] = {
 #ifdef SDL_CAMERA_DRIVER_V4L2
     &V4L2_bootstrap,
 #endif
+#ifdef SDL_CAMERA_DRIVER_PIPEWIRE
+    &PIPEWIRECAMERA_bootstrap,
+#endif
 #ifdef SDL_CAMERA_DRIVER_COREMEDIA
     &COREMEDIA_bootstrap,
 #endif

src/camera/SDL_syscamera.h

@@ -205,6 +205,7 @@ typedef struct CameraBootStrap
 // Not all of these are available in a given build. Use #ifdefs, etc.
 extern CameraBootStrap DUMMYCAMERA_bootstrap;
 extern CameraBootStrap V4L2_bootstrap;
+extern CameraBootStrap PIPEWIRECAMERA_bootstrap;
 extern CameraBootStrap COREMEDIA_bootstrap;
 extern CameraBootStrap ANDROIDCAMERA_bootstrap;
 extern CameraBootStrap EMSCRIPTENCAMERA_bootstrap;