ci: add codeowner group for migrations (#36661)
ci: add codeowner group for migrations (#36661)

Adds a new codeowner group that is dedicated for changes
to the migrations stored in `packages/core/schematics`.

PR Close #36661

IdeaBlade/angular,wKoza/angular,angular/angular,gdi2290/angular,shairez/angular,mgechev/angular,IdeaBlade/angular,manekinekko/angular,gdi2290/angular,manekinekko/angular,ocombe/angular,ocombe/angular,ocombe/angular,alxhub/angular,shairez/angular,filipesilva/angular,brandonroberts/angular,gnomeontherun/angular,gnomeontherun/angular,mgechev/angular,gdi2290/angular,IdeaBlade/angular,alxhub/angular,filipesilva/angular,wKoza/angular,gkalpak/angular,wKoza/angular,ocombe/angular,brandonroberts/angular,JiaLiPassion/angular,ocombe/angular,wKoza/angular,gdi2290/angular,gdi2290/angular,angular-indonesia/angular,ocombe/angular,alxhub/angular,mgechev/angular,JiaLiPassion/angular,angular-indonesia/angular,blesh/angular,angular/angular,JiaLiPassion/angular,wKoza/angular,JiaLiPassion/angular,alxhub/angular,angular/angular,gkalpak/angular,matsko/angular,IdeaBlade/angular,angular-indonesia/angular,mgechev/angular,brandonroberts/angular,filipesilva/angular,manekinekko/angular,manekinekko/angular,matsko/angular,mgechev/angular,brandonroberts/angular,matsko/angular,blesh/angular,angular-indonesia/angular,angular/angular,gdi2290/angular,filipesilva/angular,IdeaBlade/angular,wKoza/angular,shairez/angular,gkalpak/angular,brandonroberts/angular,blesh/angular,gnomeontherun/angular,gnomeontherun/angular,shairez/angular,manekinekko/angular,blesh/angular,brandonroberts/angular,matsko/angular,blesh/angular,filipesilva/angular,alxhub/angular,shairez/angular,manekinekko/angular,matsko/angular,gkalpak/angular