Fix / tweak blog category display

Author: ryyppy

_blogposts/2020-08-28-new-rescript-logo.mdx

@@ -2,6 +2,7 @@
 author: made_by_betty
 date: "2020-08-27"
 title: "A New Logo for ReScript"
+category: "ecosystem"
 previewImg: https://res.cloudinary.com/dmm9n7v9f/image/upload/v1598616442/Reason%20Association/rescript-lang.org/Art-3-rescript-launch_ovoibg.jpg
 articleImg: https://res.cloudinary.com/dmm9n7v9f/image/upload/v1598616442/Reason%20Association/rescript-lang.org/ReScript-3_by4q2u.jpg
 description: |

src/Blog.js

@@ -338,7 +338,7 @@ let default = (props: props): React.element => {
           {Belt.Array.mapWithIndex(rest, (i, post) => {
             let badge = post.frontmatter.badge->Js.Null.toOption
             let category =
-              first.frontmatter.category
+              post.frontmatter.category
               ->Js.Null.toOption
               ->Belt.Option.map(category => category->BlogFrontmatter.Category.toString)