Update the main title

Author: yunseo-kim

_config.yml

@@ -14,7 +14,7 @@ timezone: Asia/Seoul
 # jekyll-seo-tag settings › https://github.com/jekyll/jekyll-seo-tag/blob/master/docs/usage.md
 # ↓ --------------------------
 
-title: Yunseo Kim's Insights           # the main title
+title: Yunseo Kim's Study Notes        # the main title
 
 tagline: Mathematics, Physics, and DS. # it will display as the subtitle