Improve functionalities of getData when dealing with arrays to retrieve array length only + entry at index

[CJ42]

I'm submitting a...

• bug report
• feature request
• question about the decisions made in the repository
• question about how to use this project

Summary

The function getData allows to query data keys of key type Array. However, it only allows to retrieve the full list of entries in the array. See code example in documentation below:

It would be useful if this function could be flexible enough to allow:

• query a single entry at a specific index:

erc725js.getData("LSP12IssuedAssets[2]")

(should also handle the case if the index is over the array length.

• query a subset in the array:

erc725js.getData("LSP12IssuedAssets[3:6]")

• querying the array length only: TBD what the function call would look like