Bitcoin Spread

This indicator display the current lowest and the highest value of btc on a set of exchanges for a define type of market.
Bitcoin Spread was originally made by @DayTradingItalia, i have bring his indicator to pine v4, add add some stuff to it:

• 5 Type of BTC Market : USDT Swap, USD and Futures (current/next contract)
  
• Spread value
  

版本注释:

small fix