Docs: split introduction & getting started sections

Signed-off-by: Solomon Hykes <solomon@dagger.io>

docs/introduction/1235-what.md

@@ -0,0 +1,26 @@
+---
+slug: /1235/what
+displayed_sidebar: "0.2"
+---
+
+# What is Dagger?
+
+Dagger is a portable devkit for CICD.
+
+Using Dagger, software teams can develop powerful CICD pipelines with minimal effort, then run them anywhere.
+
+## Benefits
+
+Benefits of using Dagger include:
+
+* Unify dev and CI environments. Write your pipeline once, Dagger will run it the same everywhere.
+* Reduce CI lock-in. No more re-writing everything from scratch every 6 months.
+* Rapid debugging of your pipelines. Dagger runs equally well on your local machine, and in CI.
+
+## How does it work?
+
+1. Automate actions with your favorite programming language. No proprietary SDK: just regular shell, Go, Javascript, Python...
+2. Reuse actions from a large and growing catalog.
+3. Tie it all together in CUE - a revolutionary declarative language invented at Google. No more YAML hell!
+4. Test and debug instantly on your local machine. No more waiting 10min to catch a typo.
+5. Run your pipelines on any Docker-compatible runtime, for maximum portability. This means most modern CI runners can run Dagger out of the box.

website/sidebars.js

@@ -11,6 +11,19 @@
 
 module.exports = {
   "0.2": [
+    {
+      type: "category",
+      label: "Introduction",
+      collapsible: false,
+      items: [
+	      "introduction/what",
+	      "introduction/vs",
+	],
+      link: {
+        type: 'generated-index',
+	title: "Dagger Documentation",
+      },
+    },
     {
       type: "category",
       label: "Getting Started",
@@ -19,7 +32,7 @@ module.exports = {
         type: 'doc',
         id: 'getting-started/index'
       },
-      items: ["getting-started/local-dev", "getting-started/ci-environment", "getting-started/vs"],
+      items: ["getting-started/local-dev", "getting-started/ci-environment"],
     },
     {
       type: "category",