It used to be easy to post info/etc files until this sites redesign.
However, it dawned on me to try posting Text info using the Code Panel in a Ftirzing project.
It works!
Attached is Fritzing file with XML for a PCB with one cutout and silkscreen.
an_XML_inCodePanel.fzz (1.4 KB)
Copy the XML text and Paste it into a Text document, save it with .svg extension.
Don’t use ‘Rich Text’, use ‘Plain’ text setting.
Then, it can be loaded into Fritzing as the PCB Image… 
Zipping (not just renaming any more, the forum looks at the file) an svg (or anything else the forum won’t accept) as a .fzpz file also works. Unzip it when you get it and the files are there. Also if your svg is large enough (small footprint type svgs get "couldn’t determine the size which probably means it was 0px by 0px) to load, the px values are too small (typically 1*1 or there about) increasing that by a factor of 10 or 100 makes the svg visible and downloadable.
Peter