Includes the following changes over the first iteration:
* [gtasks] Fix unittests
* [gtasks] Move docstrings before vars in GTasksItem, unrelated: Add
ruff linter in dev-dependencies
* [gtasks] Run `generate-shell-completions`
* [docs][gtasks]
* Refer to Taskwarrior in capitalized in READMEs
* [gtasks] Add help page to main README
* [gtasks] Reduce code duplication between gtasks and gcal sides
* [gtasks] get_all_items to also list completed items (+gcal)
* [gtasks] Fix completion of tasks from gtasks -> TW
* [gcal] Remove unused method, correct typehints usage in gcal internals
* [aggregator] Correct typos
* [gtasks] Fix synchronization of due dates, notes
* [gtasks] Update demo gif
* [gtasks] Fix bug with single-letter title events not getting sync-ed properly
* [gtasks] Add note re the due dates in Google Tasks
* [gtasks] Use the "update" dates to trigger a sync
* [gtasks] Mark an item as changed if a date is different for more than
1 minute - until now it was 10mins