Add `ctrl/cmd + k` Keyboard Shortcut

[ryanleichty]

Added support for ctrl/cmd + k keyboard support for opening the search dialog in the primitives docs (https://www.radix-ui.com/primitives/docs/overview/introduction). This is probably the most common keyboard shortcut on most doc sites.

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This pull request:

• [ ] Fixes a bug
• [x] Adds additional features/functionality
• [ ] Updates documentation or example code
• [ ] Other