Update README.md

Author: peterdey

README.md

@@ -1,12 +1,18 @@
 # MQTTNotifier
-Windows 10 background application that creates Toast Notifications from MQTT messages.
+Lightweight Windows 10 background application that creates Toast Notifications from MQTT messages.
 
+Designed intentionally for simplicity & portability:
+- .NET Framework 4.5.2: probably even runs on Windows 8 (not tested)
+- No additional runtimes, libraries or dependencies
+- Portable: no installation required
+
+![Screenshot of Windows 11 Toast Notification](screenshot.png "Screenshot of Windows 11 Toast Notification")
+
+## Message formats
 Supports two message formats:
 - Raw: Message text appears as the content
 - JSON (HomeAssistant format): `{"title": "Message title", "message": "Hello world!"}`
 
-![Screenshot of Windows 11 Toast Notification](screenshot.png "Screenshot of Windows 11 Toast Notification")
-
 # Usage
 The program folder can be placed anywhere (e.g. C:\Program Files\MQTTNotifier)
 
@@ -15,5 +21,12 @@ Add a shortcut to `MQTTNotifier.exe` in your Startup folder (optional)
 # Configuration
 All configuration is in `MQTTNotifier.exe.config` - which must be located beside the executable itself.
 
+# Building
+The build toolchain that comes with Windows works:
+```bat
+PATH=%PATH%;C:\Windows\Microsoft.NET\Framework\v4.0.30319
+msbuild
+```
+
 # Credits
 Uses the M2MQTT library: https://www.nuget.org/packages/M2Mqtt/