Add ERC: Decentralized Employment System

[jamesavechives]

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[eip-review-bot]

File ERCS/erc-7750.md

Requires 1 more reviewers from @g11tech, @SamWilsn, @xinbenlv

[SamWilsn]

The biggest blocker for getting this one merged is that the specification section is too informal and lacking in detail.