Division by zero

[xandrefreire]

Hello,

Thank you for this library.

Potential unhandled crash: Division by Zero

I have identified a runtime crash issue caused by division by zero. For instance, the following code snippet causes the library to crash:

let rule =
"""
{ "/" : [10, 0] }
"""

// Example parsing
let result: String? = try? JSONLogicClient.applyRule(rule, to: nil)

print("result = \(String(describing: result))")

This pull request #33 implements a fix to prevent this crash.