DevOps: automate weekly contributors list updates

[nlebovits]

Describe the task

Transition away from using the all-contributors bot to a more efficient implementation for managing contributors. The new implementation should improve automation and workflow by:

1. Automating a weekly check for new contributors.
2. Opening a single PR per week that includes all new contributors.
3. Opening the PR against the staging branch instead of main.

The new implementation should still follow a similar formatting to all-contributors for how the information is displayed in the README. It can either totally abandon all-contributors or find a better way of using it.

Acceptance Criteria

• Automate a weekly check for new contributors.
• Open a single PR per week that includes all new contributors.
• Open the PR against the staging branch.
• Display contributor information in the README with a format similar to all-contributors.

Additional context

• For reference, see the All Contributors documentation.