• add contrib.discord (similar to contrib.telegram) (#976)
• add contrib.bells to auto-enable all extras
• add contrib.utils_worker for common slow tasks (e.g. web I/O)
  • fix lazy large memory usage & discard unsent messages (unprocessed tasks)
• fix slow notebook imports (#955 <- #709)
• fix gui TypeError on unknown len() (#971)
• misc documentation/error message updates
  • more succinct ImportError on missing ipywidgets (#872)
  • fix broken/deprecated link (#981)
  • add inline usage for contrib.discord and contrib.telegram
• misc framework updates
  • add official py3.8 support (#986)
  • fix snap builds