Accessing Market Data

[CoinGecko API](https://www.coingecko.com/en/api) is a solid choice, and what we used for Balancer project. Open to other suggestions. From here we can get asset values in any fiat currency, as well as price action within a timeframe.

They also have a nice [Javascript wrapper lib](https://github.com/miscavage/CoinGecko-API) already

* Will we need to consider rate limits / API keys here?
* Free tier is 100 requests / minute.

#### What data do we need?
For each asset:
* Current price (in USD)
* 24 hour change

You can make one call `/coin/:id` but there is a ton of extraneous data

Inizia dalla documentazione collegata della CoinGecko API e dal wrapper JavaScript, concentrandoti sull’endpoint /coin/:id e sui relativi requisiti di rate limit. L’issue non indica file o test del repository; il lavoro sarà pronto solo dopo aver concordato e documentato i campi richiesti per asset e l’approccio per API-key o volume di richieste.

Scritto dal modello di indicizzazione a partire dal testo della issue.