feat: implement toHaveSelection

[silviuaavram]

What:
Implement toHaveSelection.

Why:
Closes #289.

How:
Based on #412.

Differences from original PR:

• changed the partial selection condition a little bit to help with testing:

else {
    // Element is partially selected
    const selectionStartsWithinElement =
      element === originalRange.startContainer ||
      element.contains(originalRange.startContainer)
    const selectionEndsWithinElement =
      element === originalRange.endContainer ||
      element.contains(originalRange.endContainer)
    selection.removeAllRanges()

    if (selectionStartsWithinElement || selectionEndsWithinElement) {
      temporaryRange.selectNodeContents(element)

      if (selectionStartsWithinElement) {
        temporaryRange.setStart(
          originalRange.startContainer,
          originalRange.startOffset,
        )
      }
      if (selectionEndsWithinElement) {
        temporaryRange.setEnd(
          originalRange.endContainer,
          originalRange.endOffset,
        )
      }

      selection.addRange(temporaryRange)
    }
  }

• added a few more asserts to the tests.
• types
• documentation

Checklist:

• Documentation
• Tests
• Updated Type Definitions
• Ready to be merged
  

[silviuaavram]

Hey @gnapse could you help me with a review here, please? Thanks!

[gnapse]

Thanks!

[gnapse]

@all-contributors please add @silviuaavram for code, test

[allcontributors]

@gnapse

I've put up a pull request to add @silviuaavram! 🎉

[github-actions]

🎉 This PR is included in version 6.6.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀