feat: identify publishable packages

[BioPhoton]

As a user of the plugin I want to be able to have a fine grained control over which packages the plugin should consider as publishable.

At the moment we can do that by adding a publishable tag in the projects project.json file:

{
  "name": "my-lib",
  // ...
  "tags": ["publishable"]
}

It would be better to be able to control and filter publishable projects over plugin options:

// nx.json
{
  "plugins": [
    {
      "plugin": "@pushu-based/nx-environments",
      "options": {
         "targets": ["publish", "nx-release-publish"]
         "tags": ["publishable"] // Optionally filter projects by tags for a more finegrained control
      }
    }
  ]
}