Update getting started doc for `dotnetup` to include daily support

### Prerequisites

- [x] I have read the [dotnetup documentation](https://github.com/dotnet/sdk/tree/release/dnup/documentation/general/dotnetup).
- [x] I have searched for [existing dotnetup issues](https://github.com/dotnet/sdk/issues?q=is%3Aissue%20state%3Aopen%20label%3Adotnetup).
- [x] I have searched for [existing dotnetup discussions](https://github.com/dotnet/sdk/discussions/categories/dotnetup).

### Issue type

Bug report

### Description

https://github.com/dotnet/sdk/blob/release/dnup/documentation/general/dotnetup/README.md this documentation does not mention the support for daily channels - so the selector is somewhat out of date. It also doesn't mention the newer daily channels such as `daily-10` or `daily-10.0.1xx` and those are powerful features. I had someone ask me for guidance on how to easily manage these installs without them being aware of `dotnetup` and I wanted to point them to this doc but it didn't mention those right away.

I think it'd be nice to add those to the doc / table and list of channels here.

### dotnetup version

_No response_