cmd/gen-docs/main.go: auto generate docs for CRD

The new make command `make gen-docs` is introduced.
It will build a markdown file from the CRD introduced by Kilo.

The generation of the docs is a requirement for building the website.

Signed-off-by: leonnicolas <leonloechner@gmx.de>

website/docs/api

@@ -0,0 +1,5 @@
+---
+id: api
+title: API
+hide_title: true
+---

website/sidebars.js

@@ -12,7 +12,7 @@ module.exports = {
     {
       type: 'category',
       label: 'Reference',
-      items: ['annotations', 'kg', 'kgctl'],
+      items: ['annotations', 'kg', 'kgctl', 'api'],
     },
     //Features: ['mdx'],
   ],