Add uSPAC10 as price identifier for EMP contract

A synthetic token that tracks the index of the 10 most active SPACs stocks can be used for speculative purposes and allows the user to earn on price movements in one of the most interesting markets without centralized intermediaries such as exchanges and brokers.
In addition, that token can be used as components associated with classical markets by other DeFi and DApp protocols, which makes it possible to scale.