fix(v2): use tag time for showing post item date (#1964)

* fix(v2): use tag time for showing post item date

* refactor: use rem for font-size

packages/docusaurus-theme-classic/src/theme/BlogPostItem/index.js

@@ -48,9 +48,9 @@ function BlogPostItem(props) {
           <Link to={permalink}>{title}</Link>
         </h1>
         <div className="margin-bottom--sm">
-          <small>
+          <time dateTime={date} className={styles.blogPostDate}>
             {month} {day}, {year}
-          </small>
+          </time>
         </div>
         <div className="avatar margin-bottom--md">
           {authorImageURL && (

packages/docusaurus-theme-classic/src/theme/BlogPostItem/styles.module.css

@@ -8,3 +8,7 @@
 .blogPostTitle {
   font-size: 3rem;
 }
+
+.blogPostDate {
+  font-size: 0.9rem;
+}