Explain how to handle Timeout on Connection Resiliency page

One way to mitigate it is by enabling idle connection resiliency.

Also mention that using the default ('ConnectRetryCount = 1') adds a 10s delay when calling `Open()` for a non-existent database, there's no delay for `OpenAsync()`.

---
#### Document Details

⚠ *Do not edit this section. It is required for docs.microsoft.com ➟ GitHub issue linking.*

* ID: 876c88d4-2972-d905-28d7-56f9e589f309
* Version Independent ID: 29002343-fa42-2f49-3362-53592039b26d
* Content: [Connection Resiliency - EF Core](https://docs.microsoft.com/en-us/ef/core/miscellaneous/connection-resiliency#feedback)
* Content Source: [entity-framework/core/miscellaneous/connection-resiliency.md](https://github.com/aspnet/EntityFramework.Docs/blob/master/entity-framework/core/miscellaneous/connection-resiliency.md)
* Product: **entity-framework**
* Technology: **entity-framework-core**
* GitHub Login: @rowanmiller
* Microsoft Alias: **divega**