Add short-form -v example to .NET CLI global options documentation

### Type of issue
Missing example

### Description
The .NET CLI global options section lists `--verbosity` but doesn’t show any example using the short-form `-v`.
It might not be clear to new users that `dotnet build -v normal` is equivalent to `dotnet build --verbosity normal`.

### Suggested fix
Add one or two short-form examples to the "Global options" section, like:
```bash
dotnet build -v quiet
dotnet publish -v detailed
Page URL
https://learn.microsoft.com/en-us/dotnet/core/tools/dotnet
Content source
https://github.com/dotnet/docs/blob/main/docs/core/tools/dotnet.md
Why this helps

Clarifies that both long and short forms are supported across CLI commands.