Next and prev post

4.1-blog-post.js

const BlogPost = ({ data, pageContext }) => {
  const { markdownRemark } = data
  const { prev, next } = pageContext

  return (
    <>
      ...

      {prev && (
        <Link to={prev.node.fields.slug}>
          {"<"} {prev.node.frontmatter.title}
        </Link>
      )}

      {next && (
        <Link to={next.node.fields.slug}>
          {next.node.frontmatter.title} {">"}
        </Link>
      )}
    </>
  )
}