[UI] Add estimated USD value to marketplace listing buy/sell flow

[bitbeckers]

Describe the feature you'd like to request

As a user, I want to see the estimated USD value of the order I'm creating/accepted, so that I save myself a load of mental math

Describe the solution you'd like

Add an estimated USD value of the total price if it isn’t a stable coin, e.g. “at a total price of 0.1 ETH (~3,428 USD)”

• Add a price feed to the API (cache for 1 minute)
• Get USD price for selected token
• Update modal info based on fetched price

Describe alternatives you've considered

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