Added category API doc

Author: coolbung

categories/README.md

@@ -0,0 +1,98 @@
+API to create and get Joomla categories
+
+## Create / Update Category
+
+```http
+POST /index.php?option=com_api&app=categories&resource=categories&format=raw
+```
+
+#### Request Params
+
+| Param Name | Required | Type | Comment  |
+| ---------- | -------- | ------- | :---- |
+| id         | NO       |  INT | Used to update an category. If empty, will create a new category.      | 
+| title      | YES      | STRING |         |
+| alias      | NO      | STRING | URL alias. Will be generated based on title if kept empty |
+| description    | NO      | STRING |        |
+| published    | NO      | INT | 1 = Published (Default) / 0 = Unpublished |
+| parent_id      | NO      | INT |  Specify a parent category id if you wish to create a subcategory |
+| language | NO | STRING | Will use the site's default language if none provided. |
+| extension | YES | STRING | Since Joomla supports using the categories extension for 3rd party components, this field specifies the extension name. Use com_content for article categories.  |
+| access | NO | INT | Access Level for Category |
+
+
+#### Response Params
+
+| Param Name | Comment |
+| ---------- | :------ |
+| success | true if the category was created, false if there was a problem |
+| message | Error mesage in case success is false |
+| data.results | Array containing a single [Category Object](#category-object) in case of success. Empty array in case of failure. |
+
+## Get Categories List
+```http
+GET /index.php?option=com_api&app=categories&resource=categories&format=raw
+```
+#### Request Params
+
+| Param Name | Required | Comment |
+| ---------- | -------- | :------ |
+| limit         | NO       | Defaults to 20        | 
+| limitstart      | NO      | Defaults to 0        |
+| filters | NO | Key value pairs of values to filter on |
+| search | NO | search key for searching category titles |
+| fields         | NO       | Defaults to id, title, created_time | 
+
+
+#### Response Params
+
+| Param Name | Comment |
+| ---------- | :------- |
+| success | true if the API call succeeds, false if there was a problem |
+| message | Error mesage in case success is false |
+| data.results | Array of [Category Objects](#category-object) in case of success. Empty array in case of failure. |
+
+
+## Get Single Category
+```http
+GET /index.php?option=com_api&app=categories&resource=categories&format=raw&id=:id
+```
+
+#### Request Params
+
+| Param Name | Required | Comment |
+| ---------- | -------- | :------ |
+| fields         | NO       | Defaults to id, title, created_time | 
+
+
+#### Response Params
+
+| Param Name | Comment  |
+| ---------- | :------- |
+| success | true if the API call succeeds, false if there was a problem |
+| message | Error mesage in case success is false |
+| data.results | Array containing a single [Category Object](#category-object) in case of success. Empty array in case of failure. |
+
+
+## Category Object
+The actual contents of the category object will vary based on which fields are requested, however the below is the list of all possible fields.
+
+```json
+{
+  "id" : "",
+  "title" : "",
+  "alias" : "",
+  "description" : "",
+  "published" : "",
+  "created_time" : "",
+  "modified_time" : "",
+  "access" : "",
+  "language" : "",
+  "created_user_id": {
+    "id" : "",
+    "name" : "",
+    "avatar" : ""
+  },
+  "language" : ""
+}
+```