feat(config/lintstagedrc): update max DocToc depth to 4

Author: jrolfs

src/config/lintstagedrc.js

@@ -4,7 +4,7 @@ const hoverScripts = resolveHoverScripts()
 const doctoc = resolveBin('doctoc')
 
 module.exports = {
-  'README.md': [`${doctoc} --maxlevel 3 --notitle`],
+  'README.md': [`${doctoc} --maxlevel 4 --notitle`],
   '*.+(js|jsx|json|yml|yaml|css|less|scss|ts|tsx|md|graphql|mdx|vue)': [
     `${hoverScripts} format`,
   ],