Adds a logo to the ss14.admin header

SS14.Admin/Pages/Shared/_Layout.cshtml

@@ -23,7 +23,9 @@
 <header>
     <nav class="navbar navbar-expand-sm navbar-toggleable-sm navbar border-bottom box-shadow mb-3">
         <div class="container">
-            <a class="navbar-brand" asp-area="" asp-page="/Index">SS14.Admin</a>
+            <a class="navbar-brand" asp-area="" asp-page="/Index">
+                <img src="~/logo.png" class="header-logo" alt="SS14.Admin logo">
+            </a>
             <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target=".navbar-collapse" aria-controls="navbarSupportedContent"
                     aria-expanded="false" aria-label="Toggle navigation">
                 <span class="navbar-toggler-icon"></span>

SS14.Admin/wwwroot/css/site.css

@@ -25,6 +25,10 @@ a.navbar-brand {
   word-break: break-all;
 }
 
+img.header-logo {
+    max-height: 3.5rem;
+}
+
 /* Provide sufficient contrast against white background */
 a {
   color: #0366d6;