docs: clarify how declaration files can be installed (#42417)
docs: clarify how declaration files can be installed (#42417)

The documentation suggested that `@types/*` scoped packages would
automatically be recognized, however the CLI configures a project such
that the package has to be explicitly added to the TypeScript
configuration files.

Closes #37572

PR Close #42417

ocombe/angular,shairez/angular,angular-indonesia/angular,JiaLiPassion/angular,brandonroberts/angular,JiaLiPassion/angular,angular-indonesia/angular,brandonroberts/angular,manekinekko/angular,angular/angular,angular-indonesia/angular,gnomeontherun/angular,mgechev/angular,angular-indonesia/angular,gnomeontherun/angular,brandonroberts/angular,gkalpak/angular,mgechev/angular,ocombe/angular,mgechev/angular,manekinekko/angular,ocombe/angular,JiaLiPassion/angular,manekinekko/angular,ocombe/angular,gnomeontherun/angular,mgechev/angular,mgechev/angular,gkalpak/angular,ocombe/angular,manekinekko/angular,manekinekko/angular,manekinekko/angular,JiaLiPassion/angular,brandonroberts/angular,shairez/angular,angular/angular,shairez/angular,ocombe/angular,shairez/angular,brandonroberts/angular,gkalpak/angular,brandonroberts/angular,gkalpak/angular,gnomeontherun/angular,angular/angular,shairez/angular,angular/angular