Update README.md

Explicitly mention the .NET Core 3.0 SDK + add hyperlinks.

README.md

@@ -49,7 +49,7 @@ How to build
 
 Windows:
 - Install Visual Studio (documented version: 16.3) with the following components:
-  - Workload ".NET Desktop Development". This includes by default .NET Framework 4.8 SDK and the .NET Framework 4.7.2 targeting pack, as well as the .NET Core 3 SDK (ILSpy.csproj targets .NET 4.7.2, and ILSpy.sln uses SDK-style projects).
+  - Workload ".NET Desktop Development". This includes by default .NET Framework 4.8 SDK and the .NET Framework 4.7.2 targeting pack, as well as the [.NET Core 3.0 SDK](https://dotnet.microsoft.com/download/dotnet-core/3.0) (ILSpy.csproj targets .NET 4.7.2, and ILSpy.sln uses SDK-style projects).
   - Workload "Visual Studio extension development" (ILSpy.sln contains a VS extension project)
   - Individual Component "MSVC v142 - VS 2019 C++ x64/x86 build tools (v14.23)" (or similar)
     - The VC++ toolset is optional; if present it is used for `editbin.exe` to modify the stack size used by ILSpy.exe from 1MB to 16MB, because the decompiler makes heavy use of recursion, where small stack sizes lead to problems in very complex methods.
@@ -64,7 +64,7 @@ Windows:
 
 Unix / Mac:
 - Make sure .NET Core 2.1 LTS Runtime is installed (you can get it here: https://get.dot.net).
-- Make sure [.NET Core 3 SDK](https://dotnet.microsoft.com/download/dotnet-core) is installed.
+- Make sure [.NET Core 3.0 SDK](https://dotnet.microsoft.com/download/dotnet-core/3.0) is installed.
 - Check out the repository using git.
 - Execute `git submodule update --init --recursive` to download the ILSpy-Tests submodule (used by some test cases).
 - Use `dotnet build Frontends.sln` to build the non-Windows flavors of ILSpy (.NET Core Global Tool and PowerShell Core).