Replace our instructions for configuring workloads with a .vsconfig

Why give instructions for this if we can just make it work
automatically!

Author: jasonmalinowski

.vsconfig

@@ -0,0 +1,9 @@
+{
+  "version": "1.0",
+  "components": [
+    "Microsoft.VisualStudio.Workload.CoreEditor",
+    "Microsoft.VisualStudio.Workload.ManagedDesktop",
+    "Microsoft.VisualStudio.Workload.NetCoreTools",
+    "Microsoft.VisualStudio.Workload.VisualStudioExtension"
+  ]
+}

Roslyn.sln

@@ -424,6 +424,12 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.VisualStudio.Lang
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "IdeBenchmarks", "src\Tools\IdeBenchmarks\IdeBenchmarks.csproj", "{FF38E9C9-7A25-44F0-B2C4-24C9BFD6A8F6}"
 EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{157EA250-2F28-4948-A8F2-D58EAEA05DC8}"
+	ProjectSection(SolutionItems) = preProject
+		.editorconfig = .editorconfig
+		.vsconfig = .vsconfig
+	EndProjectSection
+EndProject
 Global
 	GlobalSection(SharedMSBuildProjectFiles) = preSolution
 		src\Compilers\VisualBasic\BasicAnalyzerDriver\BasicAnalyzerDriver.projitems*{2523d0e6-df32-4a3e-8ae0-a19bffae2ef6}*SharedItemsImports = 4

docs/contributing/Building, Debugging, and Testing on Windows.md

@@ -24,14 +24,6 @@ The minimal required version of .NET Framework is 4.7.2.
 1. Run Restore.cmd
 1. Open Roslyn.sln
 
-If you already installed Visual Studio and need to add the necessary work loads or move to Preview 4:
-do the following:
-
-- Run the Visual Studio Installer from your start menu. You can just search for "Visual Studio Installer". If you can't find it, it's typically located at "C:\Program Files (x86)\Microsoft Visual Studio\Installer\vs_installer.exe"
-- The Visual Studio installation will be listed under the Installed section
-- Click on the menu icon (three horizontal lines), click Modify
-- Choose the workloads listed above and click Modify
-
 ## Running Tests
 
 There are a number of options for running the core Roslyn unit tests: