Update technique/mongo using mongoose with Typescript.

Author: thiagodsantos

content/techniques/mongo.md

@@ -6,6 +6,7 @@ Start by installing the required dependencies:
 
 ```bash
 $ npm install --save @nestjs/mongoose mongoose
+$ npm install --save-dev @types/mongoose
 ```
 
 Once the installation process is complete, we can import the `MongooseModule` into the root `AppModule`.