Feature: download specification (#21)

* feat: download specification

* refactor: spacing in json

coinbase.json

@@ -13,5 +13,23 @@
 	"order-types": [ "Market", "Limit", "Stop Market",  "Stop Limit" ],
 	"assets": [ "Crypto Spot" ], 
 	"brokerage-url": "https://www.coinbase.com/",
-	"documentation": "/docs/v2/cloud-platform/live-trading/brokerages/coinbase"
+	"documentation": "/docs/v2/cloud-platform/live-trading/brokerages/coinbase",
+	"module-specification": {
+		"download": {
+			"data-types": [
+				"Trade"
+			],
+			"resolutions": [
+				"Minute",
+				"Hour",
+				"Daily"
+			],
+			"security-types": [
+				"Crypto"
+			],
+			"markets": [
+				"Coinbase"
+			]
+		}
+	}
 }