Update README text w/ guidance from flod

Author: pdehaan

README.md

@@ -32,7 +32,7 @@ $ redis-server /usr/local/etc/redis.conf
 
 ## Localization
 
-Firefox Send localizations are managed via [Pontoon](https://pontoon.mozilla.org/projects/test-pilot-firefox-send/).
+Firefox Send localization is managed via [Pontoon](https://pontoon.mozilla.org/projects/test-pilot-firefox-send/), not direct pull requests to the repository. If you want to fix a typo, add a new language, or simply know more about localization, please get in touch with the [existing localization team](https://pontoon.mozilla.org/teams/) for your language, or Mozilla’s [l10n-drivers](https://wiki.mozilla.org/L10n:Mozilla_Team#Mozilla_Corporation) for guidance.
 
 ## Contributing