[UUF] NER dataset article needs example

### Type of issue

Missing information

### Description

No example of how to format the data in the text files so Key info file had to have each entity name on its own new line. For the training data file, after many hours, I still haven't worked out if the sentence is first followed by the label/entity, start position, end position and if this is repeated for each entity in the sentence. A simple text example would have clarified all this immediately.

### Page URL

https://learn.microsoft.com/en-us/dotnet/machine-learning/how-to-guides/ner-dataset-guide

### Content source URL

https://github.com/dotnet/docs/blob/main/docs/machine-learning/how-to-guides/ner-dataset-guide.md

### Document Version Independent Id

e5e56fad-4fcc-181d-74a4-0889b4e54dcb

### Platform Id

5e58c5fd-e2a3-21f0-e1b7-7f23d07c8c98

### Article author

@zewditu

### Metadata

* ID: e9d4e704-b7d6-8ed1-b49e-340a4f2db3db
* PlatformId: 5e58c5fd-e2a3-21f0-e1b7-7f23d07c8c98
* Service: **dotnet-ml**

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