Simplify doc generation infra

PUBLISHED_FROM=80e77fda1c358294f251ca77d3dd64e8ca9160e5

docs/design-concept/intro.md

@@ -1,5 +1,10 @@
 ---
 title: Design Concept
+items:
+  - { type: file, name: memory-buffers.md }
+  - { type: file, name: event-handler.md }
+  - { type: file, name: events.md }
+  - { type: file, name: conn-flags.md }
 ---
 
 Mongoose is a multi-protocol networking library that implements non-blocking,

docs/design-concept/items.json

@@ -1,9 +0,0 @@
-{
-  "items": [
-    { "type": "markdown", "name": "intro.md" },
-    { "type": "markdown", "name": "memory-buffers.md" },
-    { "type": "markdown", "name": "event-handler.md" },
-    { "type": "markdown", "name": "events.md" },
-    { "type": "markdown", "name": "conn-flags.md" }
-  ]
-}