Add Blazor test app.

Tests/MQTTnet.Test.BlazorApp/Client/Shared/MainLayout.razor

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+@inherits LayoutComponentBase
+
+<div class="sidebar">
+    <NavMenu />
+</div>
+
+<div class="main">
+    <div class="top-row px-4">
+        <a href="http://blazor.net" target="_blank" class="ml-md-auto">About</a>
+    </div>
+
+    <div class="content px-4">
+        @Body
+    </div>
+</div>

Tests/MQTTnet.Test.BlazorApp/Client/Shared/NavMenu.razor

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+<div class="top-row pl-4 navbar navbar-dark">
+    <a class="navbar-brand" href="">MQTTnet.Test.BlazorApp</a>
+    <button class="navbar-toggler" @onclick="ToggleNavMenu">
+        <span class="navbar-toggler-icon"></span>
+    </button>
+</div>
+
+<div class="@NavMenuCssClass" @onclick="ToggleNavMenu">
+    <ul class="nav flex-column">
+        <li class="nav-item px-3">
+            <NavLink class="nav-link" href="" Match="NavLinkMatch.All">
+                <span class="oi oi-home" aria-hidden="true"></span> Home
+            </NavLink>
+        </li>
+        <li class="nav-item px-3">
+            <NavLink class="nav-link" href="counter">
+                <span class="oi oi-plus" aria-hidden="true"></span> Counter
+            </NavLink>
+        </li>
+        <li class="nav-item px-3">
+            <NavLink class="nav-link" href="fetchdata">
+                <span class="oi oi-list-rich" aria-hidden="true"></span> Fetch data
+            </NavLink>
+        </li>
+    </ul>
+</div>
+
+@code {
+    private bool collapseNavMenu = true;
+
+    private string NavMenuCssClass => collapseNavMenu ? "collapse" : null;
+
+    private void ToggleNavMenu()
+    {
+        collapseNavMenu = !collapseNavMenu;
+    }
+}

Tests/MQTTnet.Test.BlazorApp/Client/Shared/SurveyPrompt.razor

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+<div class="alert alert-secondary mt-4" role="alert">
+    <span class="oi oi-pencil mr-2" aria-hidden="true"></span>
+    <strong>@Title</strong>
+
+    <span class="text-nowrap">
+        Please take our
+        <a target="_blank" class="font-weight-bold" href="https://go.microsoft.com/fwlink/?linkid=2127996">brief survey</a>
+    </span>
+    and tell us what you think.
+</div>
+
+@code {
+    // Demonstrates how a parent component can supply parameters
+    [Parameter]
+    public string Title { get; set; }
+}