better description and added subtitle for blog index page

Author: kalwalt

blog/index.html

@@ -1,8 +1,9 @@
 ---
 layout: blog
 title: WebARkit org Blog index | The official blog of WebARkit
+subtitle: WebAR articles and all about Augmented Reality
 date: 2020-09-18
-description: blog index page
+description: WebARkit blog index page; we present our articles about WebARKit and WebAR, and the news around these topics.
 image: ./resources/webarkit-logo-social.jpg
 seo:
    type: BlogPosting