Add configuration option so action can run ``dotnet restore`` for us.

Description: Currently we all have to have shell, powershell, bash, or even use command prompt in github actions in order to run dotnet restore before build + test + pack. I usually run dotnet restore first so that way it speeds up the CI and sometimes I cache the restored output to speed up future CI’s and update it if the cache is outdated due to something like an updated dependency.

Justification: This use case of this is so then users like me who do this as part of speeding up the CI could use the action to execute this command and so that way it makes their workflows smaller, more readable and maintainable.

Are you willing to submit a PR?

If possible, yes.

[vsafonkin]

Hi @AraHaan, thank you for your proposal. In my opinion, restoring of nuget packages is not in the scope of setup-dotnet task functionality and restore operation will be better to execute explicitly as separated step.

[vsafonkin]

@AraHaan https://github.com/actions/setup-dotnet/issues/206#issuecomment-864096990