add FSE decoding tables for predefined distributions to spec
add FSE decoding tables for predefined distributions to spec

They can so serve as a sample result of the table construction algorithm.

ds77/zstd,inikep/zstd,Cyan4973/zstd,inikep/zstd,Majlen/zstd,Majlen/zstd,Cyan4973/zstd,inikep/zstd,Majlen/zstd,Cyan4973/zstd,ds77/zstd,ds77/zstd,Cyan4973/zstd,inikep/zstd,Cyan4973/zstd,ds77/zstd,Majlen/zstd