README Downloads: the Windows installer lets you pick the folder (#466)

README.md

@@ -264,7 +264,9 @@ send us right now.
 | arm64 (Snapdragon and other ARM PCs) | `effectcraft-<ver>-windows-arm64.msi` | `effectcraft-<ver>-windows-arm64-portable.zip` |
 | x86 (32-bit) | `effectcraft-<ver>-windows-x86.msi` | `effectcraft-<ver>-windows-x86-portable.zip` |
 
-Installers and executables are code-signed.
+Installers and executables are code-signed. The installer asks where to install EffectCraft
+(Program Files by default), and later versions install into the same folder. To install silently
+into a folder of your choice: `msiexec /i effectcraft-<ver>-windows-x64.msi /qn INSTALLFOLDER="D:\Apps\EffectCraft"`.
 
 ### macOS