Fix docs on Alicloud builder

- Fix the link to instance types page.
- Disk configurations should go into `image_disk_mappings` array.
- If `io_optimized` is not set, it's always `false`. (NOT inferred by instance type)

website/source/docs/builders/alicloud-ecs.html.md

@@ -35,9 +35,9 @@ builder.
     can also be sourced from the `ALICLOUD_REGION` environment variables.
 
 -   `instance_type` (string) - Type of the instance. For values, see [Instance
-    Type Table](). You can also obtain the latest instance type table by invoking
-    the [Querying Instance Type
-    Table](https://intl.aliyun.com/help/doc-detail/25620.htm?spm=a3c0i.o25499en.a3.6.Dr1bik)
+    Type Table](https://www.alibabacloud.com/help/doc-detail/25378.htm?spm=a3c0i.o25499en.a3.9.14a36ac8iYqKRA).
+    You can also obtain the latest instance type table by invoking the [Querying
+    Instance Type Table](https://intl.aliyun.com/help/doc-detail/25620.htm?spm=a3c0i.o25499en.a3.6.Dr1bik)
     interface.
 
 -   `image_name` (string) - The name of the user-defined image, \[2, 128\] English
@@ -80,6 +80,9 @@ builder.
     duplicated existing image, the source snapshot of this image will be delete
     either.
 
+-   `image_disk_mappings` (array of image disk mappings) - Add one or more data disks
+    to the image.
+
     -   `disk_name` (string) - The value of disk name is blank by default. \[2, 128\]
         English or Chinese characters, must begin with an uppercase/lowercase letter
         or Chinese character. Can contain numbers, `.`, `_` and `-`. The disk name
@@ -116,9 +119,8 @@ builder.
 
 -   `zone_id` (string) - ID of the zone to which the disk belongs.
 
--   `io_optimized` (boolean) - I/O optimized.
-
-    Default value: false for Generation I instances; true for other instances.
+-   `io_optimized` (boolean) - Whether an ECS instance is I/O optimized or not.
+    The default value is `false`.
 
 -   `force_stop_instance` (boolean) - Whether to force shutdown upon device restart.
     The default value is `false`.