Auto-detect language

[joeflack4]

Description

About half of the PMA2020 global team is French-speaking. We would like to automatically detect the user's preferred language (based on browser preferences, or however best to implement this feature).

For now, we do not need to change the user interface based on the detected language. Nor do we have to add an API like the Google Translate API. Right now, simply adding the detection is enough. Later on, there will be a separate issue created when we have decided how to implement the preferred language.

Additional information (Datalab specific)

In Datalab, we already have a French language implementation. I would like you to make it so that "Français" is automatically selected when the app loads, if the users language preference is French.