C API: add equivalent of playdate.datastore.writeImage()

In my app, I'd like to write images generated by my C code to disk for later use, but I'm unaware of any way to do this directly from C without reimplementing the .pdi format. Currently, since the C code is being called from Lua, I'm able to push the LCDBitmap to stack, then use playdate.datastore.writeImage() from Lua in order to accomplish the task, but I can't imagine this is optimal for performance. Ideally, a similar function would exist in the C API. For context, I'm building a music player app in Lua and C, and I want to process and save resized and dithered album art at startup.

Thanks.

Thanks for the feedback! It does seem like we should have some way to persist images to disk.