Documenting optional method parameters?

[SjonHortensius]

There are a few optional method parameters which are not included in the schema. Would you be interested in a PR to fix that?

It's a very small list (most parameters are required):

• eth_call/1
• eth_estimateGas/1
• eth_getBalance/1
• eth_getStorageAt/2
• eth_getTransactionCount/1

I propose to include {"methods":{"__optional":{"eth_call":[1],"eth_estimateGas":[1]}} to document this

[SilentCicero]

I'll need to think about this, this has been brought up before. And would be some bigger changes in ethjs-query. Will consider.