Rustdoc: Help dialog doesn't open when the `?` key is not behind Shift

[runiq]

I'm using a weird keyboard layout which doesn't put the ? key behind Shift, which stopped me from ever viewing the help popup in Rustdoc. If I had managed to open the help popup, I would have learned about the incredibly useful type-based search feature much sooner. 👍

As far as I can tell, the code responsible is here: It's checking for ev.shiftKey unconditionally, but I believe it's only supposed to check when ev.key is undefined.

[GuillaumeGomez]

I added a button to show the help yesterday in #75366. However, it shouldn't fail like this. Sending a fix.