[frontend/pages] Add loading and error state views to about page

Iceshrimp.Frontend/Pages/About.razor

@@ -43,6 +43,18 @@
 {
     <i>Not found</i>
 }
+@if (State == State.Loading)
+{
+    <HeadTitle Text="@Loc["Loading"]"/>
+
+    <div class="loading"><LoadingSpinner Scale="2" /></div>
+}
+@if (State == State.Error)
+{
+    <HeadTitle Text="@Loc["Error"]"/>
+
+    <div>Failure</div>
+}
 
 @code {
     [Parameter] public string?                          NoteId    { get; set; }

Iceshrimp.Frontend/Pages/About.razor.css

@@ -11,4 +11,11 @@ summary {
 
 summary:hover {
     background-color: var(--hover-color);
+}
+
+.loading {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    padding-top: 25vh;
 }