What is the `@extend` directive and how is it used?
Description : Purpose and usage of `@extend`.
Answer :
`@extend` is used inSASS to inherit styles from one selector into another, which helps in reducing code duplication. For example,if you have `.base { font-size: 16px; }` and you use `.special { @extend .base; color: blue; }`,`.special` will inherit `font-size: 16px;`from`.base` and also apply `color: blue;`.