[BUGish] Add language selector to UI

[aeolianeth]

Currently, we do a best-guess for the language that should be used in the interface.

We need an explicit way for users to select their desired language.

Possible approaches

• dropdown
• text links
• a combination of the above (have a dropdown, but include text links at the bottom

Good resource on UX of language selection: https://www.smartling.com/resources/101/language-selector-best-practices/

[aeolianeth]

Moving this to Notion:

https://www.notion.so/juicebox/Add-Language-Selector-to-UI-a43dabba950148b1816a280918727880