[feat] ProgramHashChanged Event

[drspacemn]

Implement the ProgramHashChanged event.

References

https://github.com/starkware-libs/cairo-lang/blob/ab6d079f0265f903630aac9287e93d9e7cfb6fcf/src/starkware/starknet/solidity/Starknet.sol#L68

[Akashneelesh]

Heyy @drspacemn I have addressed this issue in the PR #13

[thomas192]

Hello, I implemented the ProgramHashChanged event you were talking about in PR #13 since I needed it to address issue #5