Version 3.4.0

• Rename the package from hashlib_codecs to convertlib. The public API is
  unchanged: update the dependency to convertlib and imports to
  package:convertlib/convertlib.dart.
• The hashlib_codecs package continues to be published as a thin re-export of
  convertlib for backward compatibility, and will be discontinued after a
  migration period.

Full Changelog: v3.3.1...v3.4.0