Update README to use Markdown for logo display (#34)

Nuget doesn't allow html at this time so use dark mode logo so it looks good in both modes.

Author: digitaldirk

README.md

@@ -1,10 +1,4 @@
-<h1>
-  <picture>
-    <source media="(prefers-color-scheme: dark)" srcset="content/MudBlazor-GitHub-NoBg-Dark.png">
-    <source media="(prefers-color-scheme: light)" srcset="content/MudBlazor-GitHub-NoBg.png">
-    <img alt="MudBlazor" src="content/MudBlazor-GitHub-NoBg.png">
-  </picture>
-</h1>
+# ![MudBlazor Logo](content/MudBlazor-GitHub-NoBg-Dark.png)
 
 # Theme Manager / Generator for MudBlazor