Add row index to provider (+ typo)

[MartinPicc]

Hi, I propose to add the row index to the provider (like a regular data repeater has). My use case is the following: I need to store properties for each file in a dedicated array. Having the index in the context provider will help me extract and display the right property for the right row. Also, I fixed a typo error.

[chungchunwang]

Hi! Thanks for contributing, this looks good. I'll merge it.