add linking to previous and next post

src/templates/blog-post.js

@@ -1,5 +1,6 @@
 import React from 'react'
 import Helmet from 'react-helmet'
+import Link from 'gatsby-link'
 import get from 'lodash/get'
 
 import Bio from '../components/Bio'
@@ -9,6 +10,7 @@ class BlogPostTemplate extends React.Component {
   render() {
     const post = this.props.data.markdownRemark
     const siteTitle = get(this.props, 'data.site.siteMetadata.title')
+    const { previous, next } = this.props.pathContext;
 
     return (
       <div>
@@ -31,6 +33,30 @@ class BlogPostTemplate extends React.Component {
           }}
         />
         <Bio />
+
+        <ul style={{
+          display: 'flex',
+          flexWrap: 'wrap',
+          justifyContent: 'space-between',
+          listStyle: 'none',
+          padding: 0,
+        }}>
+          { previous && (
+            <li>
+              <Link to={previous.fields.slug} rel="prev">
+                ← {previous.frontmatter.title}
+              </Link>
+            </li>
+          ) }
+
+        { next && (
+          <li>
+            <Link to={next.fields.slug} rel="next">
+              {next.frontmatter.title} →
+            </Link>
+          </li>
+        ) }
+        </ul>
       </div>
     )
   }