Format documentation strings properly & refactor MetadataMd (#1858)

* Format docs strings properly

* Refactor MetadataMd

docs/.vuepress/config.js

@@ -68,6 +68,7 @@ module.exports = {
       },
       {
         title: 'Substrate defaults',
+        path: '/substrate/',
         collapsable: false,
         sidebarDepth: 0,
         children: [

docs/substrate/storage-known-section.json

@@ -0,0 +1,26 @@
+{
+  "name": "substrate",
+  "description": "These are keys that are always available to the runtime implementation",
+  "items": [
+    {
+      "name": "changesTrieConfig(): `u32`",
+      "summary": "Changes trie configuration is stored under this key."
+    },
+    {
+      "name": "childStorageKeyPrefix(): `u32`",
+      "summary": "Prefix of child storage keys."
+    },
+    {
+      "name": "code(): `Bytes`",
+      "summary": "Wasm code of the runtime."
+    },
+    {
+      "name": "extrinsicIndex(): `u32`",
+      "summary": "Current extrinsic index (u32) is stored under this key."
+    },
+    {
+      "name": "heapPages(): `u64`",
+      "summary": "Number of wasm linear memory pages required for execution of the runtime."
+    }
+  ]
+}

docs/substrate/storage-known.md

@@ -1,23 +0,0 @@
-
----
-
-## substrate
-
-_These are keys that are always available to the runtime implementation_
-
-### changesTrieConfig(): `u32`
-- **summary**: Changes trie configuration is stored under this key.
-
-### childStorageKeyPrefix(): `u32`
-- **summary**: Prefix of child storage keys.
-
-### code(): `Bytes`
-- **summary**: Wasm code of the runtime.
-
-### extrinsicIndex(): `u32`
-- **summary**: Current extrinsic index (u32) is stored under this key.
-
-### heapPages(): `u64`
-- **summary**: Number of wasm linear memory pages required for execution of the runtime.
-
----