Remove menu_separator before the first navbar item

[DanChaltiel]

Hi,

This is a very minor PR to fix a very minor bug.

When the "Articles" navbar menu has sections, a separator is added before the section.

However, for the first section, this doesn't look very nice, as you can see for example on https://roxygen2.r-lib.org/:

The PR simply checks that the index is not 1.

Since the second argument of imap() was named index I used it, but maybe purrr::map2(navbar, seq_along(navbar), ...) would be more robust, as this might break in the case where navbar has names. I'm not familiar enough with the API to know if this can happen.

[maelle]

Merci @DanChaltiel! I agree it's ugly as it is now. 💅

Maybe there should be a code comment or an explaining variable (whose value would be index != 1)

I don't understand what you mean by the navbar having names?

[DanChaltiel]

@maelle An explaining variable is a good idea, I'm on it!

I don't understand what you mean by the navbar having names?

IIUC, imap(navbar) loops over navbar and names(navbar), and defaults to the index when navbar is unnamed. If it is possible that navbar has names at that point, index would be a character and not a numeric, and my test index != 1 would fail.

The alternative with map2() is explicit on using the index and not the names.