Add support for condition

[funbiscuit]

Hi! I've seen there was a PR #12 that tried to add support for condition but was using unmaintained libraries. How about using rhai? It is feature-rich, maintained and fit for the purpose. Adding support for condition looks like a very important thing that is currently missing and makes port much less appealing than the original app. I think I can create a PR adding a support for it but wanted to check first what would you think.