Modify BLIP2 pretraining config files to add more dataset

[xfgao]

Thanks for the great work!

The BLIP-2 paper mentions that the model is pre-trained on a combination of dataset, including COCO, Visual Genome, CC, SBU and LAION.

Looking at the provided config files, however, it seems only coco_caption and vg_caption are used.

To produce the results, do we need to modify the config files and add the other dataset?