Provide mechanism to extend mysql image with additional SQL init scripts

Please provide mechanism to extend this image by providing additional SQL scripts to be executed upon initial server startup.

See official postgres image for example on how this can be done (“How to extend this image” section in readme).

You can arrange special directory for SQL files. All *.sql files found in that directory shall be appended to $TEMP_FILE that will be passed as --init-file parameter to MySQL.