docs: Update sponsor branding

Author: linkdotnet

README.md

@@ -44,10 +44,10 @@ A huge thank you to the [sponsors of bUnit](https://github.com/sponsors/bUnit-de
 <table border="0">
 	<tr>
 		<td align="center" width="250">
-			<a href="https://www.lambdatest.com/?utm_source=bunit&utm_medium=sponsor" target="_blank">
-				<img src="https://www.lambdatest.com/blue-logo.png" style="vertical-align: middle;" width="250" height="45" />
+			<a href="https://www.testmu.ai/?utm_source=bunit&utm_medium=sponsor" target="_blank">
+				<img src="docs/site/sponsors/testmu.png" style="vertical-align: middle;" width="250" height="45" />
 				<br />
-				LambdaTest				
+				TestMu AI
 			</a>
 		</td>
 	</tr>

docs/site/index.md

@@ -51,10 +51,10 @@ bUnit is available on NuGet in various incarnations. Most users should just pick
 A huge thank you to the [sponsors of bUnit](https://github.com/sponsors/egil). The higher tier sponsors are:
 
 <div class="d-flex flex-row mb-3 align-items-center">
-  <a href="https://www.lambdatest.com/?utm_source=bunit&utm_medium=sponsor" target="_blank" class="d-block p-3 text-center">
-    <img src="https://www.lambdatest.com/blue-logo.png" style="vertical-align: middle;" width="250" height="45" />
+  <a href="https://www.testmu.ai/?utm_source=bunit&utm_medium=sponsor" target="_blank" class="d-block p-3 text-center">
+    <img src="sponsors/testmu.png" style="vertical-align: middle;" width="250" height="45" />
     <br />
-    LambdaTest				
+    TestMu AI
   </a>
 </div>