Align standalone links design with the Design System.

Standalone default links are displayed in certain blocks such as columns block (images + icons style) after a text paragraph.

Tasks:

• add new states for each standalone link (default, external & PDF links) = focus / visited / visited hover.
• change the link & icons color for hover & onclick (active) states
• Add a "a title" attribute to help users predict what will happen if they follow certain links(for external + PDF links) => e.g: the link will lead to The Guardian website / the link will open a PDF file.
• Add a chevron icon for the default link  + implement it as a SVG inline icon instead of font icon.
• Replace external and PDF icons with the new ones in the Design system + implement them as SVG inline icons instead of font icons.