Add documentation for a common JSON transaction parameters object

[rwalworth]

An issue was noticed while working on hiero-ledger/hiero-sdk-cpp#695 (with #205) that it isn't exactly clear when an additional signature should be applied to a transaction for some tests. The use of the signerKey field should be used to explicitly provide the keys that should sign a transaction.

[rwalworth]

In addition to allowing signerKeys to be a list and an explicit way to provide extra signatures to a transaction, the scope of this issue is being expanded to create and document a JSON object which will contain all common transaction parameters which can easily be added to our JSON-RPC APIs. This object should include transactionId, maxTransactionFee, etc. This will allow us to test these properties going forward and keeping them documented and consolidated.