ADD : [config] 형관펜 밑줄 효과 스타일링 추가

Author: dev-splin

assets/css/jekyll-theme-chirpy.scss

@@ -2,7 +2,7 @@
 ---
 
 @use 'main
-{%- if jekyll.environment == 'production' -%}
+{%- if jekyll.environment == ' production ' -%}
   .bundle
 {%- endif -%}
 ';
@@ -12,3 +12,7 @@
 }
 
 /* append your custom style below */
+.highlighting-underline {
+  background: linear-gradient(transparent 60%, #1b99f3 80%);
+  padding: 2px 4px;
+}