resolve failure to update locale

[dragarcia]

The following error pops up in the recent Dockerbuild:

#8 3698.5 perl: warning: Setting locale failed. #8 3698.5 perl: warning: Please check that your locale settings: #8 3698.5	LANGUAGE = (unset), #8 3698.5	LC_ALL = (unset), #8 3698.5	LANG = "en_US.utf8" #8 3698.5 are supported and installed on your system. #8 3698.5 perl: warning: Falling back to the standard locale ("C"). 

which then prevents the PG image from going up properly:

supabase-db | bash: warning: setlocale: LC_ALL: cannot change locale (en_US.UTF-8) supabase-db | The files belonging to this database system will be owned by user "postgres". supabase-db | This user must also own the server process. supabase-db | supabase-db | initdb: error: invalid locale settings; check LANG and LC_* environment variables supabase-db exited with code 1 

Proposed fix is taken from this stack overflow question.