adding filename form field + updating echo package to v4 (#57)

build/docs/content/09-scalability.md

@@ -0,0 +1,27 @@
+---
+title: Scalability
+---
+
+The API being stateless, you may scale it as much as you want.
+
+For instance, using the following Docker Compose file:
+
+```yaml
+version: '3'
+
+services:
+
+  # your others services
+
+  gotenberg:
+    image: thecodingmachine/gotenberg:4
+```
+
+You may now launch your services using:
+
+```bash
+$ docker-compose up --scale gotenberg=your_number_of_instances
+```
+
+When requesting the Gotenberg service with your client(s), Docker will automatically
+redirect a request to a Gotenberg container according to the round-robin strategy.