New param signature for effects & guards

[cassiozen]

• Adds access to context from whithin effects
• Renames update to setContext
• Changes parameter signature for both Effects and Guards to an object.

In E.g.: Instead of this:

effect(_, update, _, context) {
    // ...
}

this:

effect({setContext, context}) {
    // ...
}

Closes #33

[github-actions]

size-limit report 📦

Path	Size
dist/usestatemachine.cjs.production.min.js	411 B (+4.85% 🔺)
dist/usestatemachine.esm.js	452 B (+5.12% 🔺)