Add "rel" attribute for links to external pages

[tom2drum]

For links lead to external pages there should be rel="noopener noreferrer" attribute.
Checks links in the footer and in the network menu.

[iamenochlee]

@tom2drum can i work on this?

[iamenochlee]

@tom2drum this shouldn't apply to slise links right?

[tom2drum]

Yes, please add it to all advertisement links and for those that open a new page with window.open.

[iamenochlee]

alright i see there are no test for link attributes, is that fine?

[iamenochlee]

@tom2drum pr here #3039