Upload of other files than images not possible

Even shown in the demo docs, it announces, that editor.js is running beneath codex.docs which is capable of handling attachments other than pictures (https://docs-demo.codex.so/codex-docs). Unfortunately it seems like codex.docs is not able to do so. Can this be added as well as the possiblity to add other plugins (maybe there might be one to have colored text :))

Start with the codex.docs demo and its Editor.js integration, which the issue identifies as the relevant entry point. Determine how attachments are currently limited to images and how additional plugins would be registered; done means non-image files and an additional plugin can be added and used successfully.

Scritto dal modello di indicizzazione a partire dal testo della issue.