Append the $PATH instead of overwriting it

Author: drake7707

release-notes/2.2/2.2.300-SDK/2.2.300-SDK-download.md

@@ -68,7 +68,7 @@ Installing from the packages detailed above is recommended or you can install fr
 
 ```bash
 mkdir -p $HOME/dotnet && tar zxf dotnet.tar.gz -C $HOME/dotnet
-export PATH=$HOME/dotnet
+export PATH=$PATH:$HOME/dotnet
 ```
 
 ## .NET Core Runtime-only installation