Info related to path arg is insufficient

### Type of issue

Missing information

### Description

The DOC doesn't specify whether the `path` is absolute or relative or can be both. In case relative can be used, it is not clear what directory will be the starting point.

### Page URL

https://learn.microsoft.com/en-us/dotnet/api/system.io.file.readalltextasync?view=net-8.0#system-io-file-readalltextasync(system-string-system-threading-cancellationtoken)

### Content source URL

https://github.com/dotnet/dotnet-api-docs/blob/main/xml/System.IO/File.xml

### Document Version Independent Id

731b377a-27dd-b3d4-67ee-1eee2b6189d3

### Article author

@dotnet-bot