Create preprocessor_config.json

Without this vllm (nightly) wont start.

preprocessor_config.json

@@ -0,0 +1,10 @@
+{                                                                              
+"image_processor_type": "Gemma3ImageProcessor",                              
+"do_resize": true,                                                           
+"size": {"height": 896, "width": 896},                                       
+"do_rescale": true,                                                          
+"rescale_factor": 0.00392156862745098,                                       
+"do_normalize": true,                                                        
+"image_mean": [0.5, 0.5, 0.5],                                               
+"image_std": [0.5, 0.5, 0.5]                                                 
+}