feat(posts): render heading 4 in TOC (#1023)

_javascript/modules/components/toc.js

@@ -1,11 +1,11 @@
 export function toc() {
-  if (document.querySelector('#core-wrapper h2,#core-wrapper h3')) {
+  if (document.querySelector('#core-wrapper h2')) {
     // see: https://github.com/tscanlin/tocbot#usage
     tocbot.init({
       tocSelector: '#toc',
       contentSelector: '.post-content',
       ignoreSelector: '[data-toc-skip]',
-      headingSelector: 'h2, h3',
+      headingSelector: 'h2, h3, h4',
       orderedList: false,
       scrollSmooth: false
     });

_posts/2019-08-08-text-and-typography.md

@@ -23,7 +23,7 @@ This post is to show Markdown syntax rendering on [**Chirpy**](https://github.co
 
 <h3 data-toc-skip>H3 - heading</h3>
 
-<h4>H4 - heading</h4>
+<h4 data-toc-skip>H4 - heading</h4>
 
 ## Paragraph
 

_sass/layout/post.scss

@@ -314,9 +314,7 @@ h1 + .post-meta {
     }
 
     ul {
-      a {
-        padding-left: 2rem;
-      }
+      padding-left: 0.75rem;
     }
   }
 }