Update README for CSPROJ tooling [Skip CI]

Author: nblumhardt

README.md

@@ -13,12 +13,10 @@ You can get started quickly with this package, and later migrate to the full Ser
 
 ### Getting started
 
-**1.** Add [the NuGet package](https://nuget.org/packages/serilog.extensions.logging.file) to the `"dependencies"` section of your `project.json` file:
+**1.** Add [the NuGet package](https://nuget.org/packages/serilog.extensions.logging.file) as a dependency of your project either with the package manager or directly to the CSPROJ file:
 
-```json
-    "dependencies": {
-        "Serilog.Extensions.Logging.File": "1.0.0"
-    }
+```xml
+<PackageReference Include="Serilog.Extensions.Logging.File" Version="1.0.1" />
 ```
 
 **2.** In your `Startup` class's `Configure()` method, call `AddFile()` on the provided `loggerFactory`.