List available projects in a workspace - `ng projects`

# 🚀 Feature request

### Command (mark with an `x`)

- [X] projects

### Description

In large Angular monorepo workspaces, it can sometimes be non-obvious to discover all the available projects which can be built. We should consider a new command (`ng projects`, `ng ls`, etc.) which lists all the projects in the current workspace. This can help new developers in workspace figure out exactly what they want to work on and how to do it.

### Describe alternatives you've considered

Workaround is to introspect the `angular.json` file, which is not obvious or easy to do, especially for a new developer.

Comece examinando como o Angular CLI lê o angular.json do workspace atual e como os comandos existentes são registrados. Compare os pontos de entrada propostos `ng projects` e `ng ls` e, em seguida, verifique se o comando escolhido lista todos os projetos disponíveis no workspace e explica como cada um pode ser usado.

Escrita pelo modelo de indexação a partir do texto da issue.