The issue requires replacing the deprecated `.extend` API in styled components with the new `styled()` function. Start by searching the codebase for all occurrences of `.extend` in component files, likely under `src/components/`. Check if there are any existing migration guides or PRs referencing this upgrade. The task is localized but requires understanding of the styled components v4 API changes.
Upgrade to styled-components@4 · gitpoint/git-point#885 | Good First Issue