Class
Common
```kotlin
value class StringAnnotation(val value: String) : AnnotatedString.Annotation
```
An `AnnotatedString.Annotation` class which holds a String `value`.
You can use it to provide a custom annotation to the `AnnotatedString`.
If you use the `AnnotatedString.Builder` methods like `withAnnotation` and provide a string
annotation, it will be automatically wrapped into this holder class.