RiotQuest automatically clones the common DataDragon json files to your computer.
Every part of RiotQuest which uses one of these assets will return the local translation.
RiotQuest ships with a local copy of the en_US DataDragon copy. If this copy is outdated (new patch released) then the library will detect this and automatically redownload the most recent version.
If you plan on using a different language than en_US then you'll change the RiotQuest locale and the new locale will automatically be downloaded.
Here's an example on how you can change the language. This function is described in detail over at Configuration
Client::setLocale('en_GB'); // Changes to british english
The download will run whenever the page is loaded. This means the page will load slower if there is static assets to download. This will only happen once though.