feat: add Link shared component

Renders Next.js Link for internal routes, plain anchor with
target="_blank" rel="noopener noreferrer" when external prop is set.

src/shared/ui/index.ts

@@ -6,6 +6,7 @@ export type { CardBackground } from './Card';
 export { Card, CardContent, CardDescription, CardFooter, CardHeader, CardSidebar, CardTitle } from './Card';
 
 export { Input, Textarea } from './Input';
+export { Link } from './Link';
 export { RichText } from './RichText';
 export type { ContainerSize, SectionBackground } from './Section';
 export { Container, Section } from './Section';