Add Review and Reviewed PR Count to Leaderboard Activity

[GODrums]

Motivation

Currently, the activity column of the leaderboard lists a developer's reviews grouped by the review's state. In order to give an even better activity overview, we are also interested in the total number of reviewed PRs and number of distinct reviewed PRs.

Description

Adds new "summary" elements to the activity column of the leaderboard consisting of:

• Number of Reviews: Sum of all reviews independent of state (includes dismissed reviews)
• Number of reviewed PRs: Count of PRs, which have been reviewed at least once
• Separator via the chevronRight icon

Screenshots (if applicable)

Checklist

General

• PR title is clear and descriptive
• PR description explains the purpose and changes
• Code follows project coding standards
• Self-review of the code has been done
• Changes have been tested locally
• Screenshots have been attached (if applicable)
• Documentation has been updated (if applicable)

Client (if applicable)

• UI changes look good on all screen sizes and browsers
• No console errors or warnings
• User experience and accessibility have been tested
• Added Storybook stories for new components
• Components follow design system guidelines (if applicable)

Server (if applicable)

• Code is performant and follows best practices
• No security vulnerabilities introduced
• Proper error handling has been implemented
• Added tests for new functionality
• Changes have been tested in different environments (if applicable)

[FelixTJDietrich]

Looks good!