Documentation: Add screenshot for WHPX

Author: https://github.com/gunnarbeutner
Commit: https://github.com/SerenityOS/serenity/commit/c3e8866118e
Pull-request: https://github.com/SerenityOS/serenity/pull/8594
Reviewed-by: https://github.com/ADKaster
Reviewed-by: https://github.com/awesomekling ✅
Reviewed-by: https://github.com/nico

Documentation/BuildInstructionsWindows.md

@@ -44,6 +44,8 @@ To run SerenityOS in a WHPX-enabled QEMU VM:
   or by running the following command in an elevated PowerShell session: \
 `dism /Online /Enable-Feature /All /FeatureName:HypervisorPlatform`
 
+![WHPX Windows Feature](WHPX_Feature.png)
+
 - Specify QEMU acceleration option: \
 `export SERENITY_VIRT_TECH_ARG="-accel whpx,kernel-irqchip=off"`