Calculate width of menu bar rather than hard coding it

[LMBishop]

See #293, related to #263

Calculate the minimum width of it before turning it into a hamburger menu, rather than us having to change the value manually each time

[lcrojano]

Hello, I am interested in resolving this issue. My plan is to compute the complete width of the menu content and adjust a media query based on it. This approach will enable you to smoothly switch to a hamburger menu whenever the screen width is insufficient to display the entire menu.