Open to a PR for RTF, TXT, DOCX, Markdown attachment support?

[timaro]

My use case demands support for formatted-text document attachments. I know that most of the APIs support RTF, Markdown, etc., and that they can theoretically be embedded inline in the text body, but it's helpful to have the MIME Type and the multipart attachment system in place.

The new Content system seems easy enough to extend to support this, but I don't have enough free time to do it for every different supported LLM. Would you be open to a PR limited to the one or two that I'm using regularly?

[crmne]

@timaro are you aware of any LLMs that support these formats?

[crmne]

Done: 8683243
docx can't be supported directly because no LLM can read it as is, but you can convert it to PDF or text with another tool and pass it to RubyLLM thanks to the code above.