IPFS in Protocol Stack

The current list of component layers in §5 lists all of the necessary components to implement DWN functionality, and the lowest level reads simply "IPFS". While I have no doubt that IPFS is the most appropriate way to host a DWN, they can also be hosted on centralized servers, torrent files, etc.

Maybe change "IPFS" to "Data Storage" and add a supplemental note below that IPFS is the recommended system for data storage? Or maybe even a section/appendix of recommended systems to implement each component in the stack, which would be more extensible. (We could recommend encryption standards, schemas, things for other components of the stack as well.)