Update checkboxlist.md (fixed a typo)

[tony-asu]

fixed typo

General tasks for a new feature (delete if not applicable)

• Check links to and from demos, demos descriptions and metadata

New Component Checklist (delete for other types of PRs)

• - Overview article

  • General information on the purpose of the component.
  • Instruction on how to add the component to a razor component.
  • Basic configuration of the component - code snippet with a scenario that is both basic, and meaningful.
  • Provide information on the component's reference.
  • List the available features for the component and/or provide links (slugs) for the articles that explain them in details. For simpler components listing parameters might be enough, for more complex ones sections with a sentence or two that links corresponding articles might be more suitable.
  • Maybe some Example(s) - very common scenarios, notes, typical use case, etc. Not mandatory, depends on the component.

• - Data binding article - applicable if data can be provided to the component. My be one article or a folder with several articles (examples - DropDownList and TreeView)

• - Feature/component specific articles - those articles explain the component specific features, which do not suit in any of the before-mentioned articles. Examples of such articles are the Navigator for the Stock Chart, the Indeterminate state for the CheckBox and others.

• - Selection article - applicable if the component exposes items selection. May be a folder.
  [ ] - Single item selection
  [ ] - Multiple item selection

• - Templates - applicable if additional customization is allowed with Templates. Usually a folder, see the grid

• - Events article - applicable if the component expose events.
  Examples of such events could be:

• OnClick
• OnChange
• ValueChanged
• SelectedItemsChanged
• OnRead
• etc.

• Update Input Validation, Globalization, Keyboard Navigation, Accessibility Compliance articles as applicable.

• Link from the Overview components list

[ntacheva]

Thank you for your contribution!