Update navbar to include logo and version display

Replaced the text-based navbar header with a logo image and added a version display below the project name. This enhances the visual identity and provides useful versioning information directly in the navigation bar.

Author: Magnus Ahlberg

docs/Linq2GraphQL.Docs/Shared/MainNavigation.razor

@@ -1,8 +1,11 @@
-<Navbar Background="NavbarBackground.Dark" Direction="NavbarDirection.Vertical">
+<Navbar Background="NavbarBackground.Dark" Direction="NavbarDirection.Vertical">
 
     <a href="https://github.com/linq2graphql/linq2graphql.client" class="navbar-brand navbar-brand-autodark">
-
-        <h2 class="text-secondary">Linq2GraphQL</h2>
+        <img src="img/logo.svg" alt="Linq2GraphQL" class="navbar-brand-image me-2">
+        <h2 class="text-secondary">
+            Linq2GraphQL
+            <div class="fs-6 lh-1 fst-italic">Version: @ThisAssembly.AssemblyFileVersion</div>
+        </h2>
     </a>
 
     <NavbarMenu>