Add translation mailing list to README.md

Link to the new translation mailing list from README.md

README.md

@@ -76,12 +76,14 @@ Translations
 Changes to translations as well as new translations can be submitted to
 [Bitcoin Core's Transifex page](https://www.transifex.com/projects/p/bitcoin/).
 
-Periodically the translations are pulled from Transifex and merged into the git repository. See the
+Translations are periodically pulled from Transifex and merged into the git repository. See the
 [translation process](doc/translation_process.md) for details on how this works.
 
-**Important**: We do not accept translation changes as github pull request because the next
+**Important**: We do not accept translation changes as GitHub pull requests because the next
 pull from Transifex would automatically overwrite them again.
 
+Translators should also subscribe to the [mailing list](https://groups.google.com/forum/#!forum/bitcoin-translators).
+
 Development tips and tricks
 ---------------------------