chore: add package license

Author: cnblogs-dudu

src/Microsoft.Extensions.Caching.ServiceStackRedis/Microsoft.Extensions.Caching.ServiceStackRedis.csproj

@@ -6,6 +6,7 @@
     <TargetFrameworks>netstandard2.0;netstandard2.1;net6.0;net7.0</TargetFrameworks>
     <AssemblyName>ServiceStackRedisCache</AssemblyName>
     <PackageTags>cache;redis;distributedcache</PackageTags>
+    <PackageLicenseExpression>Apache-2.0</PackageLicenseExpression>
     <PackageProjectUrl>https://github.com/cnblogs/ServiceStackRedisCache</PackageProjectUrl>
     <RepositoryType>git</RepositoryType>
     <RepositoryUrl>https://github.com/cnblogs/ServiceStackRedisCache</RepositoryUrl>