Add a DRAFTS section to the Europa docs sidebar

This is meant to act as catch-all for pages that have been written
ad-hoc, but don't currently fit anywhere.

While it was initially mentioned that this should be called
Knowledgebase, it didn't seem to accurately describe the intent.
The email & message default DRAFTS seemed better, so I just went with it.

Signed-off-by: Gerhard Lazu <gerhard@lazu.co.uk>

website/sidebars.js

@@ -108,6 +108,15 @@ module.exports = {
         "use-cases/svelte-vercel",
       ],
     },
+    {
+      type: "category",
+      label: "DRAFTS",
+      collapsible: true,
+      collapsed: true,
+      items: [
+        "learn/api",
+      ],
+    },
     {
       type: "link",
       label: "🕸  pre-Europa 🕸",