Restore documentation on .NET Framework 4.7.2 support

Author: ralish

README.md

@@ -36,7 +36,12 @@ While the the records WHEA emits can be seen through its event log channels, the
 Requirements
 ------------
 
-- .NET 8 Runtime - you can install it with winget, `winget install Microsoft.DotNet.Runtime.8`
+- A supported .NET runtime, either:
+  - .NET Framework 4.7.2 (or newer)  
+    *Built-in since Windows 10 1803 and Server 2019*
+  - .NET 8 (or newer)  
+    Install manually: [Download](https://dotnet.microsoft.com/en-us/download/dotnet/8.0) and run the installer  
+    Install with WinGet: `winget install Microsoft.DotNet.Runtime.8`
 
 Usage
 -----