feat: add postgres-driver typings

Author: lvauvillier

packages/cubejs-postgres-driver/driver/index.d.ts

@@ -0,0 +1,8 @@
+import { PoolConfig } from "pg";
+
+declare module "@cubejs-backend/postgres-driver" {
+  class PostgresDriver {
+    constructor(options?: PoolConfig);
+  }
+  export = PostgresDriver;
+}

packages/cubejs-postgres-driver/package.json

@@ -12,6 +12,7 @@
     "node": ">=8.11.1"
   },
   "main": "driver/PostgresDriver.js",
+  "typings": "driver/index.d.ts",
   "scripts": {
     "lint": "eslint **/*.js"
   },