Generating token for publishing

Author: FeodorFitsner

CONTRIBUTING.md

@@ -11,4 +11,22 @@ Bump version in:
 Bump `serious_python` dependency version with `flutter pub get` in example lock files:
 
 * `example/flet_example/pubspec.lock`
-* `example/flask_example/pubspec.lock`
+* `example/flask_example/pubspec.lock`
+
+Update `CHANGELOG.md`.
+
+## Getting token for automatic publishing to pub.dev
+
+Token locations on different OSes: https://stackoverflow.com/a/70487480/1435891
+
+Login to pub.dev:
+
+```
+flutter pub login
+```
+
+Encode token to base64:
+
+```
+cat $HOME/Library/Application\ Support/dart/pub-credentials.json | base64
+```