Add header link to discord.js documentation (discordjs#241)

Closes #239

Author: Whiteaj36

guide/.vuepress/config.js

@@ -33,6 +33,10 @@ const config = {
 text: 'Commando',
 link: '/commando/',
 },
+{
+text: 'Discord.js Documentation',
+link: 'https://discord.js.org/#/docs/main/stable/general/welcome',
+},
 ],
 sidebar,
 },