Pdobacz proposes Opcode Extension for Multiverse Compatibility Upgrade

Ethereum protocol developer pdobacz proposes EIP-7702, reserving `EXTENSION (0xae)` opcode for extensions on other EVM chains. This ensures the opcode won't become valid on Ethereum L1 EVM, but can be used as a prefix in other EVMs. The proposal opens up extension possibilities and allows successful ones to be back-ported into Ethereum 1.0. As of Feb. 17, no external reviews or open issues exist.