Add Jandex index

[javier-godoy]

Feature proposal

Add a Jandex index as requested in #83 (comment)

Describe solution expectations

I already submitted a PR in FlowingCode/AddonsDemo#84, so I'm just creating this issue so that it can be triaged.

Additional information

https://github.com/FlowingCode/AddonsInternal/issues/38.