ImageIO writer error: neither save nor fileio_save is defined

[antoine-levitt]

Occurs when running the example in the README in a notebook with a clean julia 1.6:

All errors:
===========================================
ImageIO writer error: neither save nor fileio_save is defined
  due to 
Errors encountered while save FileIO.Stream{FileIO.DataFormat{:PNG}, IOContext{Base64.Base64EncodePipe}, Nothing}(IOContext(Base64.Base64EncodePipe(IOBuffer(data=UInt8[...], readable=true, writable=true, seekable=true, append=false, size=0, maxsize=Inf, ptr=1, mark=-1), Base64.Buffer(UInt8[0x03, 0x00
etc

Possibly similar to JuliaIO/FileIO.jl#310