Add DexTrade client (v0.13.0)

[martinkersner]

This PR introduces DexTrade client accessible from Datamaxi.datamaxi. It provides two methods get and exchanges to receive the DEX trade data and supported exchanges, respectively.

Example of fetching WKLAY-KPING trading data from kaiaswap

The get method supports pagination parameters: page, limit and sort. To learn more details visit https://python.datamaxiplus.com/dex-trade

from datamaxi import Datamaxi

api_key = "YOUR API KEY"
maxi = Datamaxi(api_key=api_key)

maxi.dex_trade.get(exchange='kaiaswap', symbol='WKLAY-KPING')

Example of fetching supported exchanges

from datamaxi import Datamaxi

# this call does not require API key
maxi = Datamaxi()

maxi.dex_trade.exchanges()