etapi support for png base64 attachment images

[Oblivionatory]

https://github.com/Nriver/trilium-py/blob/main/src/trilium_py/client.py#L1217
https://github.com/TriliumNext/Trilium/blob/main/apps/server/src/etapi/attachments.ts
https://github.com/zadam/trilium-web-clipper/blob/master/trilium_server_facade.js

Clipper is detecting base64, then converting it to buffer,
but in eatpi, on new attachment, if mime type is image/png, and role is image or content is data:image/png;base64,
it is not converting to buffer using base64, resulting in broken images, if I am right, it is converting as string UTF8, which is the main cause.

is it possible to fix it without breaking other things, thanks alot.