add filter for "PaidPost" keyword

[madMac74]

IMHO, the situation has become more dramatic than just classical, small ads in the corner: 
there are now full pages, paid by third party, insidiously infiltrating the editorial content on news websites 
(and printed paper as well, but unfortunately the extension won't work there…). 

For instance: 

• https://www.euronews.com/paidpost/philip-morris/think-again/EN-index.html
• https://www.ft.com/paidpost/credit-suisse/edtechs-bright-future.html
• https://paidpost.newyorker.com/questionsmatter

[dgraham]

This is a bit outside the scope of the block list that Ka-Block! maintains. We block only at the domain level to keep the block list fast and easy to maintain.