message: fix(platform-browser): add missing peerDependency on `@angular/animations`
  `@angular/platform-browser/animations` has a dependency on `@angular/animations` however, this is not listed in `peerDependencies`
  With this change we add this package as an optional peerDependency as it's only required when using the `@angular/platform-browser/animations` entrypoint.
  Fixes
  PR Close
diff: "author": "angular",
  "license": "MIT",
  "peerDependencies": {
  + "@angular/animations": "0.0.0-PLACEHOLDER",
  "@angular/core": "0.0.0-PLACEHOLDER",
  "@angular/common": "0.0.0-PLACEHOLDER",
  "tslib": "^1.10.0"
  },
  + "peerDependenciesMeta": {
  + "@angular/animations": {
  + "optional": true
  + }
  + },
  "repository": {
  "type": "git",
  "url": "https://github.com/angular/angular.git",
  