Update wsl-config.md to document the dnsProxy option (#1920)

dnsProxy is a wls2 configuration option which we need to document for customers that need to turn off the NAT DNS proxy.

WSL/wsl-config.md

@@ -221,6 +221,7 @@ This file can contain the following options that affect the VM that powers any W
 | debugConsole | boolean* | `false` | Boolean to turn on an output console Window that shows the contents of `dmesg` upon start of a WSL 2 distro instance. Only available for Windows 11.|
 | nestedVirtualization | boolean* | `true` | Boolean to turn on or off nested virtualization, enabling other nested VMs to run inside WSL 2. Only available for Windows 11.|
 | vmIdleTimeout | number* | `60000` | The number of milliseconds that a VM is idle, before it is shut down. Only available for Windows 11.|
+| dnsProxy | bool | true | Only applicable to networkingMode = NAT. Boolean to inform WSL to configure the DNS Server in Linux to the NAT on the host. Setting to false will mirror DNS servers from Windows to Linux. |
 | networkingMode** | string | NAT | If the value is `mirrored` then this turns on mirrored networking mode. Default or unrecognized strings result in NAT networking. |
 | firewall** | bool | true | Setting this to true allows the Windows Firewall rules, as well as rules specific to Hyper-V traffic, to filter WSL network traffic. |
 | dnsTunneling** | bool | false | Changes how DNS requests are proxied from WSL to Windows |