yarn add @postlight/parser fails (wrong package name in README?)

[fungilation]

Expected Behavior

yarn add should work.

Current Behavior

README has

yarn add @postlight/parser

Running that results in

yarn add @postlight/parser 
yarn add v1.22.19
[1/5] 🔍  Resolving packages...
error An unexpected error occurred: "https://registry.yarnpkg.com/@postlight%2fparser: Not found".
info If you think this is a bug, please open a bug report with the information provided in "/Users/gfung/Documents/code/WonderSwipe/yarn-error.log".
info Visit https://yarnpkg.com/en/docs/cli/add for documentation about this command

Steps to Reproduce

yarn add @postlight/parser

Detailed Description

Is package @postlight/parser, or @postlight/mercury-parser? It's been the latter for a long while.

Also, latest version is 2.2.2 on github, but that's not on npm yet (latest on npm is 2.2.1)