docs(pubspec): 📖 add issue_tracker and topics

Signed-off-by: Albert Mañosa <26429103+albertms10@users.noreply.github.com>

pubspec.yaml

@@ -1,8 +1,14 @@
 name: music_notes
-description: Comprehensive set of utilities for working with music theory concepts.
+description: A comprehensive Dart library for effortlessly working with music theory concepts.
 version: 0.17.1
 
 repository: https://github.com/albertms10/music_notes.git
+issue_tracker: https://github.com/albertms10/music_notes/issues
+topics:
+  - music
+  - music-theory
+  - education
+  - midi
 
 environment:
   sdk: ">=3.3.0 <4.0.0"