Support quickly moving focus to search

[parlough]

pub.dev should support a shortcut to quickly move focus to the search bar. On the home and search pages, this would be the larger one, and on other pages, the one in the navbar.

Support "/" on all platforms, "Cmd+K" on macOS, and "Ctrl+K" on non-mac platforms

[sigurdm]

Support "/" on all platforms, "Cmd+K" on macOS, and "Ctrl+K" on non-mac platforms

Do we have documentation on why these are the exact keys?

[isoos]

On the landing page and on the search page we auto-focus on the search bar, and on other pages we do have support for "/".
I'm a bit unsure about the Ctrl/Cmd+K shortcut, as it seems to be used by Chrome as a default searchbar operation, and it seems to be not ideal to catch that. Note: Github seems to support only "/".