Clarifies that the endIndex for slice isn't included. 

Other JS references clarify this and I found myself tripping on it today since it wasn't obvious.
Fix typo in `unordered list`
Merge pull request #3930 from CodingFu/patch-1

Fix typo in `unordered list`
Merge pull request #3928 from MiguelMadero/document-slice

Clarifies that the endIndex for slice isn't included.