📖 add section on Trust Proxy configuration in dotenv.mdx

pages/docs/configuration/dotenv.mdx

@@ -42,6 +42,20 @@ For more info see:
   ]}
 />
 
+### Trust proxy
+Use the address that is at most n number of hops away from the Express application. 
+req.socket.remoteAddress is the first hop, and the rest are looked for in the X-Forwarded-For header from right to left. 
+A value of 0 means that the first untrusted address would be req.socket.remoteAddress, i.e. there is no reverse proxy.
+The `TRUST_PROXY` environment variable default is set to `1`.
+
+Refer to [Express.js - trust proxy](https://expressjs.com/en/guide/behind-proxies.html) for more information about this.
+
+<OptionTable
+  options={[
+    ['TRUST_PROXY', 'number', 'Specifies the number of hops.', 'HOST=1'],
+  ]}
+/>
+
 ### Static File Handling
 
 <OptionTable