Don't require a dotnet-tools.json in every consumer project (OSOE-883)

[Piedone]

In a consumer theme project, if you want to use Lombiq.Hosting.MediaTheme.Deployer during build to automatically build a deployment package, you need to add a .config/dotnet-tools.json file like this:

{
  "version": 1,
  "isRoot": true,
  "tools": {
    "lombiq.hosting.mediatheme.deployer": {
      "version": "3.0.0-alpha.5.nest-407",
      "commands": [
        "media-theme-deploy"
      ]
    }
  }
}

This also includes a reference to Lombiq.Hosting.MediaTheme.Deployer's version, something you have to manually keep up-to-date.

Instead, let's get rid of requiring every consumer project such a file somehow. Perhaps we can have only a single file in Lombiq.Hosting.MediaTheme.Targets? Note that this should work even if all the Media Theme projects are consumed from NuGet.

Jira issue