docs: update migration content (#43964)
docs: update migration content (#43964)

Update content for AngularJS to Angular migration.  Add note to manually create UMD bundles.

PR Close #43964

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