Add nuget restore post actions

[Mrxx99]

This adds a nuget restore post action to the project templates.
It is currently not added for the xplat templates because there the experience is not great if you do not have all the workloads installed as e.g. Android, iOS and web fail

CLI output

I wanted to specifiy that only the shared and Desktop project should be restored, but there seems to be a bug in templating so this does not work (dotnet/templating#5922).

We could already merge it without the xplat templates if you want and add the xplat templates later, when the issue is fixed in the SDK.

[Takoooooo]

Works good,but i am curious why this parameter isn't displayed in the CLI and it isn't displayed in the VS? Also may you add it to the readme because otherwise people wouldn't ever know it exists

[Mrxx99]

Added the option to the readme.
It is displayed in CLI:

And in VS it is not displayed because it is not added to the ide.host.json what was intentional as the nuget restore post action is ignored by IDEs (at least VS) as you can read here: https://github.com/dotnet/templating/wiki/Post-Action-Registry#restore-nuget-packages

[Takoooooo]

LGTM,thanks!