docs: add documentation on how to use `from_signature` method

[Aviksaikat]

Overview

Provide a simple overview of what you wish to see added. Please include:

• What you are trying to do: trying to get the MethoABI using from_signature method.
• Why Ape's current functionality is inadequate to address your goal: N/A

Specification

• Examples like this

# get methodabi from function signature
import ethpm_types
method_abi = ethpm_types.abi.MethodABI.from_signature("function_name(uint256 arg1)")
# get methodabi from Events signature
signature = "Transfer(address indexed from, address indexed to, uint256 value)"
event = EventABI.from_signature(signature)
print(event.name)
>> Transfer

Dependencies

N/A

[linear[bot]]

APE-1781 docs: add documentation on how to use `from_signature` method