Open menu links to external websites in a new tab

[ihalaij1]

Description

What?

Open menu links to external websites, such as https://google.com in a new tab, instead of in the current tab.

Why?

This problem was pointed out by a teacher.

Fixes #1392

[murhum1]

Seems to work fine - having to assign the separate is_external_menu_url_flag variable just for one if statement feels a bit clunky, but at least according to a quick google search it doesn't look like there's a better alternative :/

[ihalaij1]

Seems to work fine - having to assign the separate is_external_menu_url_flag variable just for one if statement feels a bit clunky, but at least according to a quick google search it doesn't look like there's a better alternative :/

Yes, I tried to do it on one line first, but it didn't work...