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>

docs/faq/1229-empty-buildkit-cache.md

@@ -0,0 +1,22 @@
+---
+slug: /1229/empty-buildkit-cache
+displayed_sidebar: europa
+---
+
+# Empty BuildKit's cache
+
+There are two ways of emptying the BuildKit cache:
+
+- Run your action with the `--no-cache` option:
+
+```console
+dagger do <your-action> --no-cache
+```
+
+- Stop and remove the buildkitd container and remove its associated volume:
+
+```console
+docker stop dagger-buildkitd ; docker rm dagger-buildkitd ; docker volume rm dagger-buildkitd
+```
+
+In 99.9% of the cases, the first solution is enough