style: adjust figcaption

Author: yoshinorin

src/styles/globals.scss

@@ -253,7 +253,8 @@ figure {
     margin: 0;
   }
   figcaption {
-    margin-top: 0.9em;
+    margin-top: 1.0em;
+    margin-bottom: 2.5em;
     text-align: center;
     font-size: map.get(variables.$font-size, normal);
     opacity: 0.7;