docs: Implement FAQ page, default values in Cue + fix sidebar and titles

Move faq pages from guide to specific FAQ page, shown as per tailscale format.
Custom in-house logic implemented because Docusaurus doesn't manage it

Signed-off-by: guillaume <guillaume.derouville@gmail.com>

website/sidebars.js

@@ -57,6 +57,19 @@ module.exports = {
       	"guides/migrate-from-dagger-0.1",
       ],
     },
+    {
+      type: "doc",
+      label: "FAQ",
+      id: "faq/index",
+      customProps: {
+        "items": [
+          { docId: "faq/empty-buildkit-cache", href: "1229/empty-buildkit-cache" },
+          { docId: "faq/better-logs", href: "1230/better-logs" },
+          { docId: "faq/always-execute", href: "1231/always-execute" },
+          { docId: "faq/chain-actions", href: "1232/chain-actions" },
+        ]
+      }
+    },
     {
       type: "category",
       label: "References",