Implement directives `appShellRender` and `appShellNoRender`

[tschaffter]

I started using the directive *appShellNoRender to conditionally render sections of the Home page when using SSR. I followed the instructions given in Read Angular Universal: a Complete Practical Guide. However, I forgot to implement these directives:

• appShellRender
• appShellNoRender

[tschaffter]

These directives will be used in many pages/libraries. Let's create a shared util library and add them to it!

nx g @nrwl/angular:lib util --directory=shared

Update the library to meet the standard of this monorepo:

• Update .eslintrc.json.
  • Add "plugin:jest/recommended" to the extends property.
  • Update the prefix allowed for directives, components, etc. Here I decided to use sage as the prefix.
• Update project.json.
  • Set the prefix to sage.
  • Add tags and implicitDependencies.

    "tags": [
    "type:util",
    "scope:shared"
    ],
    "implicitDependencies": []

Let's create the directives:

nx g @nrwl/angular:directive directives/app-shell-render --project shared-util
nx g @nrwl/angular:directive directives/app-shell-no-render --project shared-util

• Copy-paste the directive code from the article.
• Export the directives in the definition of the shared util module.
• Import the shared util modules in the Home page module and the challenge registry app module.