Weekly newsletter - Top Active questions of week, Top Answered / Accepted questions of week, Most Voted Q&A etc

## Is your feature request related to a problem? Please describe

As of today. Answer only support following notifications

1. Q&A they participated
2. All Q&A
3. Q&A of followed Tags

problem with 2 and 3 is high email bills on admins and too much annoying for the users, so mostly disabled

## Describe the solution you'd like

Weekly newsletter which user can subscribe to - Top Active questions of week, Top Answered / Accepted questions of week, Most Voted Q&A etc

## Describe alternatives you've considered

A clear and concise description of any alternative solutions or features you've considered.

No files, tests, or entry points are named. Start by locating the existing notification, email, and user-subscription flows, then determine how weekly activity, answered or accepted questions, and voted Q&A are calculated. Done means users can subscribe to a weekly newsletter, receive the listed summaries, and avoid the excessive notification volume described.

Written by the indexing model from the issue text.