feat: Add filtering for usernames on user-contributions

[jpmcb]

Description

Followup to #58

Adds filtering for users on the user-contributions command

❯ ./build/pizza insights user-contributions \
    https://github.com/open-sauced/api \
    https://github.com/open-sauced/app \
    --users jpmcb,brandonroberts

https://github.com/open-sauced/api
User           Total      Commits    PRs Created
brandonroberts 4          0          4
jpmcb          5          0          5

https://github.com/open-sauced/app
User           Total      Commits    PRs Created
brandonroberts 368        334        34
jpmcb          6          5          1

What type of PR is this? (check all applicable)

• 🍕 Feature
• 🐛 Bug Fix
• 📝 Documentation Update
• 🎨 Style
• 🧑‍💻 Code Refactor
• 🔥 Performance Improvements
• ✅ Test
• 🤖 Build
• 🔁 CI
• 📦 Chore (Release)
• ⏩ Revert

Related Tickets & Documents

Closes #57 - decided against adding a whole extra command since this actually gets us pretty close by just adding a filter. Can continue to iterate based on feedback.

Mobile & Desktop Screenshots/Recordings

Added tests?

• 👍 yes
• 🙅 no, because they aren't needed
• 🙋 no, because I need help

Added to documentation?

• 📜 README.md
• 📓 docs.opensauced.pizza
• 🍕 dev.to/opensauced
• 📕 storybook
• 🙅 no documentation needed

[optional] Are there any post-deployment tasks we need to perform?

[optional] What gif best describes this PR or how it makes you feel?

[brandonroberts]

🍕