Document the `eth_maxPriorityFeePerGas` API method

[bgravenorst]

Document the eth_maxPriorityFeePerGas API which returns an estimate of how much priority fee, in wei, you need to be included in a block.

See: hyperledger/besu#7194

[m4sterbunny]

PR in for review> #1621 (review)

[m4sterbunny]

Postman already out of date >> decision=no update