fix(overmind): return result from transition callback

Author: christianalfoni

packages/node_modules/overmind/src/statemachine.ts

@@ -82,12 +82,14 @@ export class StateMachine<Base extends IState, States extends TStates, State ext
       Object.assign(this, newState)
       this.state = state
 
+      let result
       if (callback) {
-        callback(this)
+        result = callback(this)
       }
 
       tree.blockMutations()
 
+      return result
     } else if (process.env.NODE_ENV === 'development' && state !== this.state) {
       console.warn(`Overmind Statemachine - You tried to transition into "${state}", but it is not a valid transition. The valid transitions are ${JSON.stringify(transitions[this.state])}`)
     } else if (process.env.NODE_ENV === 'development' && state === this.state) {