Edit index.json to add a new language.
The object's key is the same name as the language forlder, file contains the json file you want the site to load.
When translating don't leave empty strings like the following image, it will also translate texts into empty strings.
So, if you want to skip some texts just delete that line.
By default the site uses jsdelivr to speed up the loading time but this will cause some delay in applying new translations.
You can use localStorage.setItem('langCdn', 'github') in the console to use github directly witch will reduce some delay time.
To change it back uses localStorage.setItem('langCdn', 'jsdelivr').