docs: add note about using NG_ASYNC_VALIDATORS (#44764)
docs: add note about using NG_ASYNC_VALIDATORS (#44764)

When setting up an async validator in a template-driven form, it's necessary to register the directive with NG_ASYNC_VALIDATORS instead of NG_VALIDATORS. This was not mentioned in the docs.
PR Close #44764

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