Actually no: `lld` is not a single linker, there has been a split between Elf/COFF folks and the MachO ones. The page you're linking is about the MachO project which is not very actively developed.
Patches are definitely welcome for MachO improvements in LLD (as always in LLVM!). You should be aware though that the Apple folks feel strongly that the original "atom" linker design is the one that they want to use. If you want to start a MachO linker based on the COFF/ELF design (which has been very successful) you will want to ping the llvm-dev mailing list first to talk with the Apple folks (CC Lang Hames and Jim Grosbach).