Add .app to README

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=199148573

README.md

@@ -16,10 +16,10 @@ domain name registrar acting on their behalf to interact with the registry.
 
 Nomulus runs on [Google App Engine][gae] and is written primarily in Java. It is
 the software that [Google Registry](https://www.registry.google/) uses to
-operate TLDs such as .GOOGLE, .HOW, .SOY, and .みんな. It can run any number of
-TLDs in a single shared registry system using horizontal scaling. Its source
-code is publicly available in this repository under the [Apache 2.0 free and
-open source license](https://www.apache.org/licenses/LICENSE-2.0).
+operate TLDs such as .google, .app, .how, .soy, and .みんな. It can run any
+number of TLDs in a single shared registry system using horizontal scaling. Its
+source code is publicly available in this repository under the [Apache 2.0 free
+and open source license](https://www.apache.org/licenses/LICENSE-2.0).
 
 ## Getting started