feat(editor): Add keyboard shortcuts for completion navigation

[metaboulie]

📝 Summary

Add Alt-J/K (Ctrl-J/K on macOS) shortcuts to navigate through the completion menu, inspired by Vim:

• Alt-J/Ctrl-J: Move down in completion list
• Alt-K/Ctrl-K: Move up in completion list

This provides a more efficient way to navigate completions without using arrow keys.

Screen.Recording.2025-01-09.at.10.55.02.mov

📋 Checklist

• I have read the contributor guidelines.
• For large changes, or changes that affect the public API: this change was discussed or approved through an issue, on Discord, or the community discussions (Please provide a link if applicable).
• I have added tests for the changes made.
• I have run the code and verified that it works as expected.

📜 Reviewers

@akshayka OR @mscolnick

[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
marimo-docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jan 9, 2025 2:42am
marimo-storybook	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jan 9, 2025 2:42am

[mscolnick]

nice!

[github-actions]

🚀 Development release published. You may be able to view the changes at https://marimo.app?v=0.10.10-dev45