fix(migrations): include nested package manifests in npm publish

Agent-Logs-Url: https://github.com/IgniteUI/igniteui-angular/sessions/77251ddd-5f46-435a-beae-3955fa968ad8

Co-authored-by: ChronosSF <2188411+ChronosSF@users.noreply.github.com>

Author: Copilot

projects/igniteui-angular/.npmignore

@@ -1,2 +1,4 @@
 # Nested package.json's are only needed for development.
-**/package.json
+**/package.json
+!migrations/package.json
+!schematics/package.json