Provide Microsoft.AspNetCore.DataProtection.EntityFrameworkCore package README (#57823)

Author: MackinnonBuck

src/DataProtection/EntityFrameworkCore/src/PACKAGE.md

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+## About
+
+`Microsoft.AspNetCore.DataProtection.EntityFrameworkCore` provides a mechanism for storing data protection keys to a database using Entity Framework Core.
+
+## How to Use
+
+To use `Microsoft.AspNetCore.DataProtection.EntityFrameworkCore`, follow these steps:
+
+### Installation
+
+```shell
+dotnet add package Microsoft.AspNetCore.DataProtection.EntityFrameworkCore
+```
+
+### Configuration
+
+To store keys in a database, use the `PersistKeysToDbContext` extension method. For example:
+
+```csharp
+builder.Services.AddDataProtection()
+    .PersistKeysToDbContext<MyDbContext>();
+```
+
+Ensure that your DB context (`MyDbContext` in the above example) implements `IDataProtectionKeyContext`. For example:
+
+```csharp
+class MyDbContext : DbContext, IDataProtectionKeyContext
+{
+    public MyKeysContext(DbContextOptions<MyKeysContext> options)
+        : base(options)
+    {
+    }
+
+    // This maps to the table that stores keys
+    public DbSet<DataProtectionKey> DataProtectionKeys { get; set; }
+}
+```
+
+## Additional Documentation
+
+For additional documentation and examples, refer to the [official documentation](https://learn.microsoft.com/aspnet/core/security/data-protection/implementation/key-storage-providers#entity-framework-core) on the Entity Framework Core key storage provider.
+
+## Feedback &amp; Contributing
+
+`Microsoft.AspNetCore.DataProtection.EntityFrameworkCore` 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).