docs(docs-infra): document the implementation of styles (incl. theming) in angular.io (#42396)
docs(docs-infra): document the implementation of styles (incl. theming) in angular.io (#42396)

PR Close #42396

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