Default docs to Europa

There are a few outstanding tasks, but they can be finished tomorrow.
This is just the beginning of many refinements, so it's all good 🙌

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

docs/getting-started/1200-local-dev.md

@@ -1,5 +1,5 @@
 ---
-slug: /1200/local-dev
+slug: /
 displayed_sidebar: europa
 ---
 

docs/introduction/1000-what_is.md

@@ -1,5 +1,5 @@
 ---
-slug: /
+slug: /1200/what/
 ---
 
 # What is Dagger?

website/sidebars.js

@@ -66,8 +66,8 @@ module.exports = {
     },
     {
       type: "link",
-      label: "🆕 Dagger Europa 🆕",
+      label: "Dagger 0.2 ➡️",
-      href: "/1200/local-dev",
+      href: "/",
     },
   ],
   europa: [
@@ -90,9 +90,7 @@ module.exports = {
         "core-concepts/plan",
         "core-concepts/client",
         "core-concepts/secrets",
-        "core-concepts/caching",
         "core-concepts/container-images",
-        "core-concepts/packages",
       ],
     },
     {
@@ -107,8 +105,8 @@ module.exports = {
     },
     {
       type: "link",
-      label: "🕸  pre-Europa 🕸",
+      label: "⬅️ Dagger 0.1",
-      href: "/",
+      href: "/1200/what/",
     },
   ],
 };