feat: add some space between 2 code blocks

Author: kiaking

src/client/theme-default/styles/code.css

@@ -23,6 +23,7 @@ div[class*='language-'] {
   border-radius: 6px;
   overflow-x: auto;
   position: relative;
+  margin: 0.85rem 0;
 }
 
 [class*='language-'] pre {