Use specific highlighters instead of including all of them. Halves the bundle size

src/highlight.js

@@ -0,0 +1,39 @@
+import visit from 'unist-util-visit';
+
+import hljs from 'highlight.js/lib/highlight';
+import python from 'highlight.js/lib/languages/python';
+import javascript from 'highlight.js/lib/languages/javascript';
+import json from 'highlight.js/lib/languages/json';
+import bash from 'highlight.js/lib/languages/bash';
+
+hljs.registerLanguage('python', python);
+hljs.registerLanguage('javascript', javascript);
+hljs.registerLanguage('json', json);
+hljs.registerLanguage('bash', bash);
+
+/**
+ * Adapted from remark-highlight.js
+ * https://github.com/ben-eb/remark-highlight.js
+ */
+export default function attacher() {
+    function visitor(node) {
+        if (!node.lang) {
+            return;
+        }
+
+        let data = node.data;
+
+        if (!data) {
+            node.data = data = {};
+        }
+
+        data.htmlContent = hljs.highlightAuto(node.value, [node.lang]).value;
+        data.htmlAttributes = data.htmlAttributes || {};
+        data.htmlAttributes.class = [
+            'hljs',
+            data.htmlAttributes.class
+        ].filter(Boolean).join(' ');
+    }
+
+    return ast => visit(ast, 'code', visitor);
+}