Clarify xUnit package version guidance in README

Updated the README to specify that Xunit.Microsoft.DependencyInjection up to 9.0.5 is for xUnit, and from 9.1.0 is for xUnit.v3. Improved formatting and wording for clarity.

Author: Arash-Sabet

README.md

@@ -10,10 +10,10 @@ This library brings in Microsoft's dependency injection container to Xunit by le
 
 ## Important: xUnit versions
 
-For xUnit packages use Xunit.Microsoft.DependencyInjection up to 9.x.x
-For xUnit.v3 packages use Xunit.Microsoft.DependencyInjection from 10.x.x
+* For **xUnit** packages use Xunit.Microsoft.DependencyInjection versions **up to** 9.0.5
+* For **xUnit.v3** packages use Xunit.Microsoft.DependencyInjection versions **from** 9.1.0
 
-Also check the [migration guide](https://xunit.net/docs/getting-started/v3/migration) from xUnit for test authors.
+Also please check the [migration guide](https://xunit.net/docs/getting-started/v3/migration) from xUnit for test authors.
 
 ## Getting started