add version property to Config for pg compatibility (#20584)

types/knex/index.d.ts

@@ -488,6 +488,7 @@ declare namespace Knex {
         debug?: boolean;
         client?: string;
         dialect?: string;
+        version?: string;
         connection?: string | ConnectionConfig | MariaSqlConnectionConfig |
             MySqlConnectionConfig | MsSqlConnectionConfig | Sqlite3ConnectionConfig | SocketConnectionConfig;
         pool?: PoolConfig;

types/knex/knex-tests.ts

@@ -22,6 +22,20 @@ var knex = Knex({
   }
 });
 
+var knex = Knex({
+  debug: true,
+  client: 'pg',
+  version: '9.5',
+  connection: {
+    user    : 'your_database_user',
+    password: 'your_database_password',
+    server  : 'your_database_server',
+    options : {
+      database: 'myapp_test'
+    }
+  }
+});
+
 var knex = Knex({
   debug: true,
   client: 'mssql',