ci: allow private packages as commit scopes

Example `fix(@angular-devkit/benchmark): bla bla`

Author: alan-agius4

.ng-dev/commit-message.ts

@@ -17,6 +17,6 @@ export const commitMessage: CommitMessageConfig = {
   minBodyLength: 0,
   minBodyLengthTypeExcludes: ['docs'],
   scopes: [
-    ...Object.keys(packages).filter(name => !packages[name].private),
+    ...Object.keys(packages),
   ],
 };

CONTRIBUTING.md

@@ -215,6 +215,7 @@ The following is the list of supported scopes:
 * **@angular/pwa**
 * **@angular-devkit/architect**
 * **@angular-devkit/architect-cli**
+* **@angular-devkit/benchmark**
 * **@angular-devkit/build-angular**
 * **@angular-devkit/build-ng-packagr**
 * **@angular-devkit/build-optimizer**