[feat] support 1x1 transparent png

[vanodevium]

How do you like the idea of adding the ability to return a 1x1 transparent png, which will be written either as a constant or as a file in the plugin and the user of the plugin will not need to save this picture, but it will be enough to specify transparent: true in the options?

Checklist

• [x] I have searched through GitHub issues for similar issues.
• [x] I have completely read through the README and documentation.