add description and usage

Author: smdn

README.md

@@ -1,10 +1,48 @@
 [![GitHub license](https://img.shields.io/github/license/smdn/Smdn.Reflection.ReverseGenerating)](https://github.com/smdn/Smdn.Reflection.ReverseGenerating/blob/main/LICENSE.txt)
 
-# `GenerateApiList` MSBuild task
+# Smdn.Reflection.ReverseGenerating.ListApi.MSBuild.Tasks
 [![NuGet Smdn.Reflection.ReverseGenerating.ListApi.MSBuild.Tasks](https://img.shields.io/nuget/v/Smdn.Reflection.ReverseGenerating.ListApi.MSBuild.Tasks.svg)](https://www.nuget.org/packages/Smdn.Reflection.ReverseGenerating.ListApi.MSBuild.Tasks/)
 
-# `list-api`
+This package provides `GenerateApiList` MSBuild task.
+
+## Usage
+```xml
+  <ItemGroup>
+    <!-- Add package reference of Smdn.Reflection.ReverseGenerating.ListApi.MSBuild.Tasks. -->
+    <PackageReference
+      Include="Smdn.Reflection.ReverseGenerating.ListApi.MSBuild.Tasks"
+      Version="1.0.3"
+      PrivateAssets="all"
+      IncludeAssets="build"
+    />
+  </ItemGroup>
+
+  <ItemGroup>
+    <!-- Specify target assemblies to generate API list. -->
+    <GenerateApiListTargetAssemblies Include="..." />
+  </ItemGroup>
+
+  <PropertyGroup>
+    <!-- (Optional) If you want to import 'Smdn.Reflection.ReverseGenerating.ListApi.MSBuild.Tasks.targets' even if the build target is `pack`. -->
+    <ExcludeRestorePackageImports>false</ExcludeRestorePackageImports>
+  </PropertyGroup>
+
+  <Target Name="GenerateApiListFromAssemblies" AfterTargets="Pack">
+    <!-- Call `GenerateApiList` task -->
+    <GenerateApiList Assemblies="@(GenerateApiListTargetAssemblies)">
+      <Output TaskParameter="GeneratedFiles" ItemName="GeneratedApiListFiles" />
+    </GenerateApiList>
+
+    <Message Text="generated API list: @(GeneratedApiListFiles)" Importance="high" />
+  </Target>
+```
+
+# Smdn.Reflection.ReverseGenerating.ListApi
 [![NuGet Smdn.Reflection.ReverseGenerating.ListApi](https://img.shields.io/nuget/v/Smdn.Reflection.ReverseGenerating.ListApi.svg)](https://www.nuget.org/packages/Smdn.Reflection.ReverseGenerating.ListApi/)
 
+This package provides `list-api` command line tool.
+
+This tool does not provide any code-formatting options.
+
 # Smdn.Reflection.ReverseGenerating
 [![NuGet Smdn.Reflection.ReverseGenerating](https://img.shields.io/nuget/v/Smdn.Reflection.ReverseGenerating.svg)](https://www.nuget.org/packages/Smdn.Reflection.ReverseGenerating/)