Add option for JSON viewer to select a key to display against an array entry in the tree

[AdyRock]

When there is a large JSON array, it would be great to be able to select a key whose value can be displayed next to the index number. At the moment I see: [0]:[Object] [1]:[Object] etc, but when the array has over 100 entries, it takes a long time to find the ones I might want to look at. If I could select a key, such as "label" and show the value: [0]:[Object] ("Don't care") [1]:[Object] ("Do Care") etc, it would be great.

[AntunBartonicek]

Can be merged with https://github.com/kapilratnani/JSON-Viewer/issues/76