Convert SAI2 to PSD

SAI version 2 format (.sai2) is proprietary and used only in the Paint Tool SAI version 2 software, which means that it is unlikely that it is supported in other graphics editors or similar format. The only way how to export these files to other graphics formats, would be to use the original software. Fortunately it supports formats from Adobe Photoshop, which means sai2 to psd conversion should be possible directly.