Inform users when Tor Browser sets their language automatically

I can think of three scenarios Tor Browser in which Tor Browser might set the language automatically (however there are probably more):

On installation, Tor Browser should set the user's language to match their system language
When the user changes their system language, Tor Browser will ????
When the user updates from a single-locale to multi-local build, Tor Browser will ????

When it sets the language automatically we'll probably want to inform the user what has happened, and deeplink to the Language section in about:preferences#general to override the setting if desired.

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