Add example to script sql statements for dotnet-ef database update

As per StackOverflow post ['how-to-get-the-database-update-script-from-the-last-migration'](https://stackoverflow.com/questions/42586235/how-to-get-the-database-update-script-from-the-last-migration):

Please add an example to the [ef docs](https://docs.microsoft.com/en-us/ef/core/cli/dotnet#dotnet-ef-database-update) on how to generated SQL file of the migration that would ocour for

```
dotnet ef migrations script -from (MigrationYouWant-1) -to MigrationYouWant
```

or provide a link to the [EF Core tools CLI Ref page](https://docs.microsoft.com/en-us/ef/core/cli/dotnet#dotnet-ef-migrations-script)

---
#### Document Details

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* ID: 4d1bdeea-0ebc-04ff-5b58-1020ad9cd72a
* Version Independent ID: 847fe92a-2940-afbf-b2ee-e68f8a8060be
* Content: [EF Core tools reference (.NET CLI) - EF Core](https://docs.microsoft.com/en-us/ef/core/cli/dotnet#dotnet-ef-migrations-add)
* Content Source: [entity-framework/core/cli/dotnet.md](https://github.com/dotnet/EntityFramework.Docs/blob/main/entity-framework/core/cli/dotnet.md)
* Product: **entity-framework**
* Technology: **entity-framework-core**
* GitHub Login: @bricelam
* Microsoft Alias: **avickers**