Introduce automatic recognition of internal or external links to the menu setting

[Tenktau]

Why Submit this change?

Take myself as an example. When I want a certain item in the menu to directly redirect to another site of mine, I encounter an error because this statement (<a href="{{ site.github.url }}/{{ item.url }}">{{ item.name }}</a>) causes my external link to be embedded behind the link of this site ({{ site.github.url }}).

How this change work?

Just a simple judgment statement was added to determine whether it meets the requirement of containing a specific string, thereby adjusting the redirection statement.

What will this change bring?

Users can directly jump to the external link (or send an email) they want by clicking the menu.

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The schematic code is as follows:

menu:
- {name: 'About', url: 'about.html'} # Visit the about page within the site
- {name: 'GitHub', url: 'https://github.com/'} # Redirect to the external link