v1.1.0

Updated:

• New grouping feature for DropdownExtended widget (#16).
  By using the grouping parameter, one can group options with headers within the dropdown.
  For more information see the example notebook.

Developer updates:

• Fixed dependabot target branch (#15).
• Update dependencies according to @dependabot (#15):
  • ipywidgets (~=7.6)
  • invoke (~=1.5)
  • pylint (~=2.7)
  • pre-commit (~=2.11)
• Update GitHub Action actions according to @dependabot (#15):
  • actions/setup-node (v2)
  • actions/cache (v2.1.4)
• Update pre-commit hooks (#15).