Added crypto snapshot endpoint (#539)

Author: ccnlui

alpaca_trade_api/rest.py

@@ -876,6 +876,12 @@ def get_latest_crypto_xbbo(self,
             api_version='v1beta1')
         return self.response_wrapper(resp['xbbo'], QuoteV2)
 
+    def get_crypto_snapshot(self, symbol: str, exchange: str) -> SnapshotV2:
+        resp = self.data_get('/crypto/{}/snapshot'.format(symbol),
+                             data={'exchange': exchange},
+                             api_version='v1beta1')
+        return self.response_wrapper(resp, SnapshotV2)
+
     def get_clock(self) -> Clock:
         resp = self.get('/clock')
         return self.response_wrapper(resp, Clock)