Add addBytes4() method to ContractFunctionParameters

[natanasow]

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👾 Description of the issue

• Currently, there are addBytes and addBytes32 but the addBytes4 method is missing in ContractFunctionParameters.java. It's needed sometimes when we want to add only a function selector for an internal call because it's always 4 bytes.

Proposed Solution:

• Add addBytes4 method that should add the input as function param to the args and if the input is not exactly 4 bytes, an error should be thrown.

• PS: The addBytes32 method could be used as a reference of what has to be done.

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