Add Alpaca Exchange impl

src/alpaca/exchange.ts

@@ -0,0 +1,18 @@
+import Alpaca from '@alpacahq/alpaca-trade-api'
+import { Exchange } from '../interface/exchange'
+
+export class AlpacaExchange implements Exchange {
+    readonly alpaca: Alpaca;
+
+    readonly name: string;
+
+    constructor(keyId: string, secretKey: string, paper: boolean) {
+        this.alpaca = new Alpaca({
+            keyId: keyId,
+            secretKey: secretKey,
+            paper: paper
+        });
+
+        this.name = 'Alpaca';
+    }
+}