add publish instruction

Author: freddycoder

README.md

@@ -10,6 +10,12 @@ C# DirectNet serial client. Use to communicate with automation direct PLC such a
 <PackageReference Include="DirectNet.Net" Version="1.0.0" />
 ```
 
+## Build a release version of the GUI app.
+
+```
+dotnet publish --sc=true -p:PublishSingleFile=true -p:DebugType=None -p:DebugSymbols=false
+```
+
 ## References
 
 https://support.automationdirect.com/docs/an-misc-029.pdf