chore: Include a README in the NuGet packages

Directory.Build.props

@@ -44,6 +44,7 @@
     <Authors>The Apache Software Foundation</Authors>
     <PackageIcon>logo_asf.png</PackageIcon>
     <PackageLicenseExpression>Apache-2.0</PackageLicenseExpression>
+    <PackageReadmeFile>README.md</PackageReadmeFile>
     <PackageProjectUrl>https://arrow.apache.org/dotnet/</PackageProjectUrl>
     <PackageTags>apache arrow</PackageTags>
     <RepositoryType>git</RepositoryType>
@@ -55,6 +56,7 @@
   <ItemGroup Condition="'$(IsPackable)' == 'true'">
     <Content Include="$(CSharpDir)LICENSE.txt" Pack="true" PackagePath="" />
     <Content Include="$(CSharpDir)logo_asf.png" Link="logo_asf.png" Pack="true" PackagePath="\" />
+    <Content Include="$(CSharpDir)src/README.md" Link="README.md" Pack="true" PackagePath="\" />
   </ItemGroup>
 
 </Project>

dev/release/verify_rc.sh

@@ -172,7 +172,10 @@ test_binary_distribution() {
   fi
 
   pushd nuget
-  for package in $(cd ../src && echo *); do
+  for package in ../src/*/; do
+    [ -d "${package}" ] || continue
+    package="${package%/}"
+    package="${package##*/}"
     for package_type in nupkg snupkg; do
       fetch_artifact "${package}.${VERSION}.${package_type}"
     done

src/README.md

@@ -0,0 +1,70 @@
+<!---
+  Licensed to the Apache Software Foundation (ASF) under one
+  or more contributor license agreements.  See the NOTICE file
+  distributed with this work for additional information
+  regarding copyright ownership.  The ASF licenses this file
+  to you under the Apache License, Version 2.0 (the
+  "License"); you may not use this file except in compliance
+  with the License.  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing,
+  software distributed under the License is distributed on an
+  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+  KIND, either express or implied.  See the License for the
+  specific language governing permissions and limitations
+  under the License.
+-->
+
+# Apache Arrow .NET
+
+[Apache Arrow](https://arrow.apache.org/) is a universal columnar format and
+multi-language toolbox for fast data interchange and in-memory analytics.
+This package is part of the .NET implementation of Apache Arrow.
+
+## Packages
+
+- `Apache.Arrow`: the core library (arrays, schemas, record batches and the
+  Arrow IPC stream and file formats).
+- `Apache.Arrow.Compression`: LZ4 frame and Zstandard codecs for compressed
+  Arrow IPC data.
+- `Apache.Arrow.Flight`: Arrow Flight client and server.
+- `Apache.Arrow.Flight.AspNetCore`: ASP.NET Core integration for Arrow Flight servers.
+- `Apache.Arrow.Flight.Sql`: Arrow Flight SQL client and server.
+- `Apache.Arrow.Operations`: codecs for the Variant binary format, including a
+  JSON reader and writer.
+- `Apache.Arrow.Scalars`: scalar types, including readers, writers and an object
+  model for the Parquet Variant binary format.
+
+## Usage
+
+Example of reading all record batches from an Arrow IPC file:
+
+```csharp
+using System.Collections.Generic;
+using System.IO;
+using System.Threading.Tasks;
+using Apache.Arrow;
+using Apache.Arrow.Ipc;
+
+public static async Task<List<RecordBatch>> ReadArrowFileAsync(string filename)
+{
+    var batches = new List<RecordBatch>();
+    using (var stream = File.OpenRead(filename))
+    using (var reader = new ArrowFileReader(stream))
+    {
+        RecordBatch batch;
+        while ((batch = await reader.ReadNextRecordBatchAsync()) != null)
+        {
+            batches.Add(batch);
+        }
+    }
+    return batches;
+}
+```
+
+## Links
+
+- Documentation: https://arrow.apache.org/dotnet/
+- Source code and issue tracker: https://github.com/apache/arrow-dotnet