docs: cleanup contributors (#28930)

- remove individuals from @angular/* package.json, we don't keep them up-to-date
- switch keys in contributors.json to GitHub handles, seems like a better identifier and lets us grab avatar images from GitHub account
- move emeritus ppl to a new Alumni group (won't yet appear on the site)
- add "lead/mentor" keys so we know who is coordinating work
- add a script that generates an "org chart" graphic

PR Close #28930

packages/compiler-cli/package.json

@@ -37,10 +37,6 @@
     "angular",
     "compiler"
   ],
-  "contributors": [
-    "Tobias Bosch <tbosch@google.com> (https://angular.io/)",
-    "Alex Eagle <alexeagle@google.com> (https://angular.io/)"
-  ],
   "license": "MIT",
   "bugs": {
     "url": "https://github.com/angular/angular/issues"
@@ -49,4 +45,4 @@
   "ng-update": {
     "packageGroup": "NG_UPDATE_PACKAGE_GROUP"
   }
-}
+}