Update README.md (#361)

Author: ardalis

README.md

@@ -1,6 +1,4 @@
-<h1 align=center>
-<img src="media/logotype 1024.svg" width=50%>
-</h1>
+![logo](media/logotype%201024.png)
 
 [![NuGet](https://img.shields.io/nuget/v/Ardalis.GuardClauses.svg)](https://www.nuget.org/packages/Ardalis.GuardClauses)[![NuGet](https://img.shields.io/nuget/dt/Ardalis.GuardClauses.svg)](https://www.nuget.org/packages/Ardalis.GuardClauses)
 ![publish Ardalis.GuardClauses to nuget](https://github.com/ardalis/GuardClauses/workflows/publish%20Ardalis.GuardClauses%20to%20nuget/badge.svg)