Use `lowercase_with_underscores` for package namesDRT-W1037

From the Pubspec format description:

DO use lowercase_with_underscores for package names.

Package names should be all lowercase, with underscores to separate words, just_like_this. Use only basic Latin letters and Arabic digits: a-z0-9_. Also, make sure the name is a valid Dart identifier -- that it doesn't start with digits and isn't a reserved word.