Update sign_raw_transaction rpc method docs

[harsenyan3]

There is a new param in sign_raw_transaction rpc to support eip-1559.
The parameter is "pay_for_gas", it is optional. Sample below:
"tx": { "to": "0x7Bc1bBDD6A0a722fC9bffC49c921B685ECB84b94".to_string(), "value": "1.234", "gas_limit": "21000", "pay_for_gas": { "tx_type": "Eip1559", "max_fee_per_gas": "1234.567", "max_priority_fee_per_gas": "1.2", }
for more info refer to KomodoPlatform/komodo-defi-framework#2051 (comment)

[smk762]

@ShantanuSharma9873 please report on progress towards this task at your earliest convenience.