feat: hljs syntax highlighting & nits

lib/core/components/Markdown/highlight.js

@@ -0,0 +1,22 @@
+const hljs = require('highlight.js');
+const chalk = require('chalk');
+const escapeHtml = require('escape-html');
+
+export default (str, rawLang) => {
+  if (rawLang === 'text') {
+    return escapeHtml(str);
+  }
+  const lang = rawLang.toLowerCase();
+  try {
+    if (hljs.getLanguage(lang)) {
+      return hljs.highlight(lang, str).value;
+    }
+  } catch (e) {
+    console.error(
+      chalk.yellow(
+        `Highlight.js syntax highlighting for language "${lang}" is not supported.`
+      )
+    );
+  }
+  return hljs.highlightAuto(str).value;
+};