Support web workers in libraries

# 🚀 Feature request

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

```
- [ ] new
- [ ] build
- [ ] serve
- [ ] test
- [ ] e2e
- [x] generate
- [ ] add
- [ ] update
- [ ] lint
- [ ] xi18n
- [ ] run
- [ ] config
- [ ] help
- [ ] version
- [ ] doc
```

### Description
I would like to use Web Workers in an Angular 8 library project.
In version 8.1.1 this seems to be supported for project type 'application' only:
```console
ng generate webWorker my-module/myWorker --project my-lib
Web Worker requires a project type of "application".
```

### Describe the solution you'd like
Generating a Web Worker should work for project type 'library' as well.

### Describe alternatives you've considered
Rewrite TypeScript worker code to JavaScript file.

Empieza ejecutando `ng generate webWorker my-module/myWorker --project my-lib` y sigue la validación del tipo de proyecto del comando generate. Se considera terminado cuando el comando genera un Web Worker para un proyecto de biblioteca en lugar de informar de que los workers requieren una aplicación.

Escrito por el modelo de indexación a partir del texto del issue.