Align body-copy links design with the Design System.

Tasks:

• add new states for each body-copy 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.
• Replace external and PDF icons with the new ones in the Design system + implement them as SVG inline icons instead of font icons.