Add batch files for testing

Add batch files to launch Visual Studio (Code) with the locally installed .NET SDK version for use with daily builds.

startvs.cmd

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+@ECHO OFF
+SETLOCAL
+
+:: This command launches a Visual Studio solution with environment variables required to use a local version of the .NET SDK.
+
+:: This tells .NET to use the same dotnet.exe that the build script uses.
+SET DOTNET_ROOT=%~dp0.dotnetcli
+SET DOTNET_ROOT(x86)=%~dp0.dotnetcli\x86
+
+:: Put our local dotnet.exe on PATH first so Visual Studio knows which one to use.
+SET PATH=%DOTNET_ROOT%;%PATH%
+
+SET sln=%~dp0ProjectEuler.sln
+
+IF NOT EXIST "%DOTNET_ROOT%\dotnet.exe" (
+    echo The .NET SDK has not yet been installed. Run `%~dp0build.ps1` to install it
+    exit /b 1
+)
+
+IF "%VSINSTALLDIR%" == "" (
+    start "" "%sln%"
+) else (
+    "%VSINSTALLDIR%\Common7\IDE\devenv.com" "%sln%"
+)

startvscode.cmd

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+@ECHO OFF
+SETLOCAL
+
+:: This command launches Visual Studio Code with environment variables required to use a local version of the .NET SDK.
+
+:: This tells .NET to use the same dotnet.exe that the build script uses.
+SET DOTNET_ROOT=%~dp0.dotnetcli
+SET DOTNET_ROOT(x86)=%~dp0.dotnetcli\x86
+
+:: Put our local dotnet.exe on PATH first so Visual Studio Code knows which one to use.
+SET PATH=%DOTNET_ROOT%;%PATH%
+
+:: Sets the Target Framework for Visual Studio Code.
+SET TARGET=net9.0
+
+SET FOLDER=%~1
+
+IF NOT EXIST "%DOTNET_ROOT%\dotnet.exe" (
+    echo The .NET SDK has not yet been installed. Run `%~dp0build.ps1` to install it
+    exit /b 1
+)
+
+IF "%FOLDER%"=="" (
+    code .
+) else (
+    code "%FOLDER%"
+)
+
+exit /b 1