fix: add peer dependencies (#49)

Author: jwillebrands

projects/testing-library/package.json

@@ -23,6 +23,9 @@
   "homepage": "https://github.com/testing-library/angular-testing-library#readme",
   "peerDependencies": {
     "@angular/common": "^8.0.0",
+    "@angular/platform-browser": "^8.0.0",
+    "@angular/animations": "^8.0.0",
+    "@angular/router": "^8.0.0",
     "@angular/core": "^8.0.0"
   },
   "dependencies": {