Add the document number "ECMA-429" to the readme (#116)

Author: andreubotella

README.md

@@ -1,9 +1,9 @@
 # Minimum common web API
 
-This repository contains the source for the current draft and all published editions of the Minimum common web API specification.
+This repository contains the source for the current draft and all published editions of ECMA-429, the WinterTC Minimum common web API specification.
 
 This specification aims to define a minimal collection of web APIs that should be implemented by server side runtimes that aim to be web-interoperable.
 
 This source is processed to obtain a human-readable version, which you can view [here](https://min-common-api.proposal.wintertc.org).
 
-The human-readable version of this specification is generated using [Bikeshed](https://speced.github.io/bikeshed).
+The human-readable version of this specification is generated using [Bikeshed](https://speced.github.io/bikeshed).