Add tag info

README.md

@@ -13,6 +13,9 @@ is clumsy
 (blessed as an _official repository_ and
 linked from [this AWS user guide](https://docs.aws.amazon.com/AmazonECR/latest/userguide/amazon_linux_container_image.html))
 
+## [Tags](https://hub.docker.com/r/quiltdata/lambda/tags)
+* `build` - introduced to build wheels per [#2](https://github.com/quiltdata/lambda/pull/2). In theory this should not affect how the environment functions, but in practice use image id `823205fae3ed` if you want to be as close to the official lambda environment as possible.
+
 ## Example: Python 3.6 deployment package
 
 ```sh