feat: subscribeAction

[deini]

Allows to listen dispatched actions

After feedback from #929 so we can implement #908

API is as suggested by @ktsn

function actionLoggerPlugin(store) {
  store.subscribeAction(({ type, payload }, state) => {
    console.log(`Before dispatching "${type}" with ${JSON.stringify(payload)}`
  })
}

const store = new Vuex.Store({
  // ...
  plugins: [actionLoggerPlugin]
})

[deini]

Made some changes to the built-in Logger plugin to play a bit more with the idea.

Not sure if I should include those changes in this PR since I'm not sure if this is something you guys want to support out of the box or would prefer going with a 3rd party actionLoggerPlugin.

Changes are here if anyone is interested.

[smithyj]

You are listening to the start of dispatch distribution，How can listening to the end of dispatch distribution?