TinyMCE uses a magic langstring only present in RTL languages which
makes it hard to automatically fetch from their strings.
Since it's the only magic string I can find a reference to (after
searching their codebase), I've elected to add this in the lang.php
serving layer. This allows us to use our own langstring instead of
re-declaring something that should be stored once across Moodle.
Part of MDL-75966
Add support for translation of the TinyMCE interface.
TinyMCE translates English language strings rather than keys, and a tool
to perform this translation is included.
David Woloszyn