SAMPLE - Add new custom data

[themandalore]

This is a sample issue for everyone to use to add a new data series of custom data (i.e. a structure never done before on tellor)

Summary - BTC bridge data

Information - Add the ability to query a bitcoin block header by block height

Return value - bytes

Supported API's / exchanges (if applicable) - BTC node

Dispute Considerations (if applicable) -chain finality