[3.38] add web-dev-config file description

src/content/platform-integration/web/web-dev-config-file.md

@@ -0,0 +1,100 @@
+---
+title: Set up a web development configuration file
+description:  Centralize web development settings including a development proxy
+short-title: Web development configuration
+---
+
+# Set up a web development configuration file
+**By Sydney Bao** 
+
+Flutter web includes a development server that defaults to serving your application in the `localhost` domain via HTTP on a randomly assigned port. While command-line arguments offer a quick way to modify the server’s behavior, this document focuses on a more structured approach: defining your server's behavior through a centralized `web_dev_config.yaml` file. This configuration file allows you to customize server settings---host, port, HTTPS settings, and proxy rules---ensuring a consistent development environment.
+
+## Create a configuration file
+
+Add a `web_dev_config.yaml` file in the root directory of your Flutter project. If you haven’t set up a Flutter project, visit [Building a web application with Flutter](https://docs.flutter.dev/platform-integration/web/building) to get started. 
+
+## Add configuration settings
+
+### Basic server configuration
+
+You can define the host, port, and HTTPS settings for your development server!
+
+```yaml
+#web_dev_config.yaml
+server:
+  host: "0.0.0.0" # Defines the binding address <string> 
+  port: 8080 # Specifies the port <int> for the development server 
+  https: 
+    cert-path: "/path/to/cert.pem" # Path <string> to your TLS certificate 
+    cert-key-path: "/path/to/key.pem" # Path <string> to TLS certificate key
+```
+
+### Custom headers
+
+You can also inject custom HTTP headers into the development server’s responses!
+
+```yaml
+#web_dev_config.yaml
+server:
+  headers: 
+    - name: "X-Custom-Header" # Name <string> of the HTTP header
+      value: "MyValue" # Value <string> of the HTTP header
+    - name: "Cache-Control"
+      value: "no-cache, no-store, must-revalidate"
+```
+
+### Proxy configuration
+
+Requests are matched in order from the `web_dev_config.yaml` file. 
+
+#### Basic string proxy
+
+Use the `prefix` field for simple path prefix matching!
+
+```yaml
+#web_dev_config.yaml
+server: 
+  proxy: 
+    - target: "http://localhost:5000/" # Base URL <string> of your backend
+      prefix: "/users/" # Path <string>
+    - target: "http://localhost:3000/"
+      prefix: "/data/"
+      replace: "/report/" # Replacement <string> of path in redirected URL (optional)
+    - target: "http://localhost:4000/"
+      prefix: "/products/"
+      replace: "" 
+```
+
+**Explanation:** 
+
+* A request to `/users/names` will be forwarded to `http://localhost:5000/users/names`.   
+* A request to `/data/2023/` will be forwarded to `http://localhost:4000/report/2023` because `replace: “/report/”` replaces the `/data/` prefix
+* A request to `/products/item/123` will be forwarded to `http://localhost:4000/item/123`. `replace: ""` removes the `/products/` prefix by replacing it with an empty string  
+
+#### Advanced regex proxy
+
+You can also use the `regex` field for more flexible and complex matching! 
+
+```yaml
+#web_dev_config.yaml
+server:
+  proxy:
+    - target: "http://localhost:5000/" 
+      regex: "/users/(\d+)/$" # Path <string> matches requests like /users/123/ 
+    - target: "http://localhost:4000/"
+      regex: "^/api/(v\d+)/(.*)" # Matches requests like /api/v1/users
+      replace: "/$2?apiVersion=$1" # Allows capture groups (optional)
+```
+
+**Explanation:** 
+
+* A request to `/users/123/` matches the first rule exactly, so it will be forwarded to `http://localhost:5000/users/123/`  
+* A request to `/api/v1/users/profile/` starts with the second rule path, so it will be forwarded to `http://localhost:4000/users/profile/?apiVersion=v1`
+
+## Configuration precedence
+
+Remember the order of precedence for settings:
+
+1. **Command-line arguments** (such as `--web-hostname`, `--web-port`)  
+2. **`web_dev_config.yaml` settings**  
+3. **Built-in default values**