Updates a file by adding a line if it doesn't already exist.

Checks if an npm package is already installed in the project.

Gets the Phoenix PubSub module from the application configuration.

Falls back to MyApp.PubSub, the module Phoenix generates, when the endpoint configuration is not loaded.

Checks if a specific string exists within a source's content.

Gets the web folder path for the Phoenix application, e.g. lib/my_app_web.