Many websites focus the search box when the forward slash/ key is pressed.

For example:

• Furo themehttps://pradyunsg.me/furo/quickstart/
• PyPIhttps://pypi.org/project/python-docs-theme/
• GitHubFocus search box when pressing slash #130
• YouTubehttps://www.youtube.com/watch?v=nMekFX2CDVk
• Discoursehttps://discuss.python.org/

Here's how PyPI implemented it:pypi/warehouse#10395