Preparations for the 1.0 release

* Less cluttered solution layout.
* Move examples to a repository of its own.
* Move Roslyn analyzer to a repository of its own.
* Enable central package management.
* Clean up csproj files.
* Add README file to NuGet packages.

src/Tests/Spectre.Console.Cli.Tests/Data/Help/RenderMarkupHelpProvider.cs

@@ -0,0 +1,11 @@
+namespace Spectre.Console.Cli.Tests.Data.Help;
+
+internal class RenderMarkupHelpProvider : HelpProvider
+{
+    protected override bool RenderMarkupInline { get; } = true;
+
+    public RenderMarkupHelpProvider(ICommandAppSettings settings)
+        : base(settings)
+    {
+    }
+}