fix: some dart publish package warnings

Author: fusion44

pubspec.yaml

@@ -3,7 +3,6 @@ description: A decoder for BOLT11 invoices
 homepage: https://github.com/fusion44/dart_bolt11_decoder
 repository: https://github.com/fusion44/dart_bolt11_decoder
 issue_tracker: https://github.com/fusion44/dart_bolt11_decoder/issues
-author: Stefan Stammberger <[email protected]>
 version: 1.0.0
 
 environment:
@@ -12,6 +11,7 @@ environment:
 dependencies:
   bech32: ^0.2.0
   decimal: ^1.3.0
+  convert: ^3.0.1
   fixnum: ^1.0.0
 
 dev_dependencies: