Improve code block style of syntax highlighting (#256)

assets/scss/_base.scss

@@ -101,15 +101,21 @@ b, strong {
   font-weight: 700;
 }
 
+.highlight > div,
+.highlight > pre {
+  margin: 0 0 2rem;
+  padding: 1rem;
+  border-radius: 1rem;
+}
+
 pre {
   display: block;
   font-family: $code-font-family;
   font-size: 1.6rem;
   font-weight: 400;
   line-height: 2.6rem;
-  margin: 2.0rem 0 2.0rem 0;
-  padding: 2.0rem;
   overflow-x: auto;
+  margin: 0;
   code {
     display: inline-block;
     background-color: inherit;
@@ -123,7 +129,6 @@ code {
   font-weight: 400;
   background-color: $alt-bg-color;
   color: $fg-color;
-  padding: 0.2rem 0.4rem 0.2rem 0.4rem;
 }
 
 blockquote {

resources/_gen/assets/scss/scss/coder.scss_5e1eb8e37c42cdfb6215b61e44dcfa5f.json

@@ -1 +1 @@
-{"Target":"css/coder.min.28d751104f30c16da1aa1bb04015cbe662cacfe0d1b01af4f2240ad58580069c.css","MediaType":"text/css","Data":{"Integrity":"sha256-KNdREE8wwW2hqhuwQBXL5mLKz+DRsBr08iQK1YWABpw="}}
+{"Target":"css/coder.min.624134b411585efffadab6a91e7d0383f0d4e22ad49de3690eccbc96f528e670.css","MediaType":"text/css","Data":{"Integrity":"sha256-YkE0tBFYXv/62rapHn0Dg/DU4irUneNpDsy8lvUo5nA="}}