update code-type of code-sample

Readme.md

@@ -4,7 +4,7 @@ Adds a EncodeToTGA Extension-Method to Texture2D. Uses Run-Length-Encoding and c
 
 As some software doesn't support RLE-Encoded TGA-Files, also supports uncompressed Encoding. The Default is RLE.
 
-```c-sharp
+```csharp
 
 Texture2D texture;