Fix checkbox UL rendering issue

[nirzaf]

Fixes #11059

Fix the markdown parser to correctly render normal UL and Checkbox UL separately.

• Assets/TinyMCE/JoplinLists/src/main/ts/core/NormalizeLists.ts

  • Add isCheckboxList function to check if a list is a checkbox list.
  • Modify normalizeLists to handle checkbox lists separately.

• Assets/TinyMCE/JoplinLists/src/main/ts/listModel/JoplinListUtil.ts

  • Correct typo in findContainerListTypeFromElement function.
  • Ensure findContainerListTypeFromElement correctly identifies checkbox lists.

• Assets/TinyMCE/JoplinLists/src/main/ts/listModel/ParseLists.ts

  • Import isCheckboxListItem from JoplinListUtil.
  • Update parseLists to handle checkbox lists separately and set the correct list type.

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[laurent22]

Hello, thank you for the PR. We also need test units for it

[laurent22]

Hello, I'm closing the PR for now, but please let me know if you would like to continue working on it