Add information about AluVM-related projects to README

[dr-orlovsky]

AluAsm (Alu assembler) makes it easier to use and debug AluVM (you can write assembly as files, not rust macros, and compile them + use libraries): https://github.com/pandoracore/aluasm

AluRE (Alu runtime environment) moves this further and provides runtime environment - but it is very early stage right now: https://github.com/pandoracore/AluRE

A concept of a high-level language for AluVM which may be used for smart contracts: https://github.com/rgb-org/contractum-lang