docs: addCollection API method

docs/.vitepress/config.js

@@ -42,6 +42,10 @@ const sidebar = [
 
 const sidebarApi = [
   { text: "Introduction", link: "/api/" },
+  {
+    text: "<code>Indiekit.addCollection</code>",
+    link: "/api/add-collection",
+  },
   {
     text: "<code>Indiekit.addEndpoint</code>",
     link: "/api/add-endpoint",

docs/api/add-collection.md

@@ -0,0 +1,18 @@
+---
+outline: deep
+---
+
+# `Indiekit.addCollection`
+
+This method is enables plug-ins to add a new collection to the MongoDB database for storing data.
+
+## Syntax
+
+```js
+new Indiekit.addCollection(name);
+```
+
+## Constructor
+
+`name`
+: Collection name. This cannot share the name of a collection added by another plug-in. Indiekit currently adds 2 collections: `posts` and `media`.

docs/api/index.md

@@ -12,6 +12,8 @@ A plug-in can provide any of the following features:
 * [content store functions](add-store.md)
 * [syndication functions](add-syndicator.md)
 
+A plug-in can also [add a collection](add-collection.md) to the MongoDb database.
+
 ## Anatomy of a plug-in
 
 A plug-in is a `Class` with an `init()` function that is used to register endpoints, presets, stores and syndicators. You can also use the `init()` function to modify Indiekit’s [configuration](../configuration/index.md). For example: