Allow specifying 'latest' as dotnet-version

[CamJN]

Description:
A workflow with the following would install the latest major version of dotnet.

    - name: Setup .NET
      uses: actions/setup-dotnet@v4
      with:
        dotnet-version: latest

Justification:
It would be nice to be able to just stick latest in the dotnet-version field and not have to update the tag when a new major version comes out. This is available in the node and ruby setup actions and is quite nice.

Are you willing to submit a PR?
Unlikely.

[aparnajyothi-y]

Hello @CamJN,
Thank you for creating this issue, we will investigate it and come back to you as soon as we have some feedback.