Very neat, a tool like this is badly needed. Also cool to see it's in rust (that means I can hack on it).

To be really useful to me though (and I would imagine others), it will need to be able to at least view (but probably edit) xlsx and/or open document format spreadsheets. I know that's a huge task, but it would add immense value to the project. I'm not asking for it and I don't feel "entitled" to it (lest the inevitable replies of "add it youself" come flying in), just trying to provide some helpful feedback.

Question: is this a project you see yourself staying committed to long term? (Obviously life events happen and things change, but at least for now, do you enjoy it? Do you use it as part of your workflow? Do you feel like it's something you'll want to own long term?)