Added gateway files

gateway/common.ts

@@ -0,0 +1,8 @@
+/**
+ * https://discord.com/developers/docs/topics/gateway#connecting-gateway-url-query-string-params
+ */
+export interface GatewayURLQuery {
+	v: string;
+	encoding: 'json' | 'etf';
+	compress?: 'zlib-stream';
+}

gateway/index.ts

@@ -0,0 +1,4 @@
+// This file exports all the types available in the recommended gateway version
+// Thereby, things MAY break in the future. Try sticking to imports from a specific version
+
+export * from './v9';