How to install ASP.NET Core Blazor Language Services when not using VS 2017?

I am learning how to build a Blazor app from this tutorial. The required tools are given as follows.

• Install the .NET Core 2.1 SDK (2.1.300-preview2-008533 or later).
• Install Visual Studio 2017 (15.7 Preview 5 or later) with the ASP.NET and web development workload selected.
• Install the latest Blazor Language Services extension from the Visual Studio Marketplace.

Because downloading and installing VS 2017 take much time, I just installed the SDK. I also downloaded the language service (.vsix file) but don't know how to install it.

The following steps succeeded.

md test
cd test


dotnet new -i Microsoft.AspNetCore.Blazor.Templates
dotnet new blazor -o ba1
cd ba1

But the following

dotnet run

produces an error as follows:

CSC : error CS1617: Invalid option '7.3' for /langversion. Use '/langversion:?' to list supported values. [C:\Users\amd\test\ba1\ba1.csproj]

Question

It seems I need to install the language service, but how can it be done without VS 2017?

Edit

For answering the comment why I did not install VS 2017 and assume (I did not assume actually) it optional, see the excerpt taken from the tutorial.