chore: add `funding` and `topics` to `pubspec.yaml` (#176)

pubspec.yaml

diff --git a/pubspec.yaml b/pubspec.yaml
index ba619f9..5ac736f 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -5,6 +5,8 @@
 issue_tracker: https://github.com/felangel/equatable/issues
 homepage: https://github.com/felangel/equatable
 documentation: https://github.com/felangel/equatable
+topics: [equality, equals]
+funding: [https://github.com/sponsors/felangel]
 
 environment:
   sdk: ">=2.12.0 <3.0.0"