New feature: support other indexes like S&P 500

[chronossc]

Please describe the problem BTC movements are usually linked to market movements that are reflected in S&P 500 and other indexes that aren't in crypto exchanges.

Describe the solution you'd like to see Would be nice to support these indexes, either by adding the resources in the menu, or by letting us add a custom resource to read data from.

Notes Thx for create crypto tracker!