Clarify why the userinfo endpoint is not statically set

src/OpenIddict.Client.WebIntegration/OpenIddictClientWebIntegrationProviders.xml

@@ -1758,13 +1758,18 @@
   <Provider Name="Osu" DisplayName="osu!" Id="924114e6-6334-4124-bbf9-46cd5458da25"
             Documentation="https://osu.ppy.sh/docs/index.html#authentication">
     <Environment Issuer="https://osu.ppy.sh/">
+      <!--
+        Note: the address of the userinfo endpoint is not set here but is dynamically computed based
+        on the game mode selected when triggering the authentication challenge. If no game mode was
+        explicitly set, the default endpoint (https://osu.ppy.sh/api/v2/me) is automatically used.
+      -->
+
       <Configuration AuthorizationEndpoint="https://osu.ppy.sh/oauth/authorize"
                      TokenEndpoint="https://osu.ppy.sh/oauth/token">
         <GrantType Value="authorization_code" />
         <GrantType Value="client_credentials" />
         <GrantType Value="refresh_token" />
       </Configuration>
-
     </Environment>
 
     <Constant Class="GameModes" Value="osu"    Name="Standard" />