Add an option to set bootloader timeout value in the "Advanced Option" screen

[bktan8]

It would be nice to be able to set the bootloader timeout value in the "Advanced Option" screen.

[mdhorn]

@bktan8 How critical do you think it is that it is settable from the installer versus just having the user use the clr-boot-manager after installation?
I'm hesitant to add this kind of dependency to the installer and would prefer the user to just set this themselves with c-b-m post-install.

[bktan8]

It's not critical, but a nice-to-have. Improved usability. It's just easier for people to know that this capability is available and can set it right then and there instead of having to dig up documentation later on.