Sort out the state of the docs

[IsaacWoods]

• [x] Get custom domain working for the project's pages
• [ ] pages: fix paths to sections on homepage (i.e. remove poplar from path: /poplar/book -> /book)
• [ ] Rewrite README to talk about multiple arches and move/remove section about previous name
• [ ] Fix formatting of homepage (menu seems to be broken? Might acc be an issue with the custom domain DNS thingy)
• [ ] Replace logo with one for Poplar
• [ ] Make book easier to maintain (merge section about kernel objects and collapse syscalls under bit in kernel section?)
• [ ] Separate out bootloader stuff into a Seed section of the book
• [ ] book: fix formatting in Ptah wire format section
• [ ] book: correct rogue PEBBLE in Capabilities section (and check code in efiloader lmao)
• [ ] book: document descriptor format for pci_get_info syscall
• [ ] book: add page in Kernel section about services (and link to from register_service syscall page)