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/Directory.Packages.props

@@ -0,0 +1,30 @@
+<Project>
+  <PropertyGroup>
+    <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally>
+  </PropertyGroup>
+
+  <ItemGroup Label="Dependencies">
+    <PackageVersion Include="MinVer" PrivateAssets="All" Version="5.0.0"/>
+    <PackageVersion Include="Microsoft.SourceLink.GitHub" PrivateAssets="All" Version="8.0.0"/>
+    <PackageVersion Include="Wcwidth.Sources" Version="2.0.0"/>
+    <PackageVersion Include="IsExternalInit" Version="1.0.3"/>
+    <PackageVersion Include="Microsoft.Extensions.DependencyInjection" Version="8.0.0"/>
+    <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.10.0"/>
+    <PackageVersion Include="Shouldly" Version="4.2.1"/>
+    <PackageVersion Include="Spectre.Verify.Extensions" Version="22.3.1"/>
+    <PackageVersion Include="Verify.Xunit" Version="26.1.6"/>
+    <PackageVersion Include="xunit" Version="2.9.0"/>
+    <PackageVersion Include="xunit.runner.visualstudio" Version="2.8.2"/>
+    <PackageVersion Include="System.Memory" Version="4.5.5" />
+    <PackageVersion Include="SixLabors.ImageSharp" Version="3.1.5" />
+
+    <PackageVersion Include="Nullable" Version="1.3.1"/>
+    <PackageVersion Include="TunnelVisionLabs.ReferenceAssemblyAnnotator" Version="1.0.0-alpha.160" />
+  </ItemGroup>
+
+  <ItemGroup Label="Static Analysis">
+    <PackageVersion Include="StyleCop.Analyzers" PrivateAssets="All" Version="1.2.0-beta.556"/>
+    <PackageVersion Include="Roslynator.Analyzers" PrivateAssets="All" Version="4.12.4"/>
+  </ItemGroup>
+
+</Project>