Provide Microsoft.Extensions.Caching.StackExchangeRedis package README (dotnet#57785)

Author: MackinnonBuck

src/Caching/StackExchangeRedis/src/PACKAGE.md

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+## About
+
+`Microsoft.Extensions.Caching.StackExchangeRedis` provides a distributed cache implementation of `Microsoft.Extensions.Caching.Distributed.IDistributedCache` using Redis.
+
+## How to Use
+
+To use `Microsoft.Extensions.Caching.StackExchangeRedis`, follow these steps:
+
+### Installation
+
+```shell
+dotnet add package Microsoft.Extensions.Caching.StackExchangeRedis
+```
+
+### Configuration
+
+To configure the Redis cache in your app, use the `AddStackExchangeRedisCache` extension method. Here's an example:
+
+```csharp
+var builder = WebApplication.CreateBuilder();
+
+builder.Services.AddStackExchangeRedisCache(options =>
+{
+    options.Configuration = builder.Configuration.GetConnectionString("MyRedisConStr");
+    options.InstanceName = "MyCache";
+});
+```
+
+## Main Types
+
+* `RedisCache`: Provides a distributed cache implementation using Redis
+* `RedisCacheOptions`: Provides options used for configuring a `RedisCache`
+
+## Additional Documentation
+
+For additional documentation and examples, refer to the [official documentation](https://learn.microsoft.com/aspnet/core/performance/caching/distributed#distributed-redis-cache) on using the Distributed Redis Cache in ASP.NET Core.
+
+## Feedback & Contributing
+
+`Microsoft.Extensions.Caching.StackExchangeRedis` is released as open-source under the [MIT license](https://licenses.nuget.org/MIT). Bug reports and contributions are welcome at [the GitHub repository](https://github.com/dotnet/aspnetcore).