How to set mode to development or production in the config file? : <p>We are migrating to webpack 4. We do have dev / prod config files already. We started getting this warning message:</p>

<pre><code>WARNING in configuration
The 'mode' option has not been set. Set 'mode' option to 'development' 
or 'production' to enable defaults for this environment.
</code></pre>

<p>We can get around this by passing --mode production in the cmdline like below:</p>

<pre><code>npm run webpack --mode development ...
</code></pre>

<p>As is mentioned on the webpack documentation, blog and everywhere else on the internet. How can we set the config in the config file? Simply putting a mode: development under modules won't work. Just a bit frustrated why the documentation is just missing...</p>
