Create a Interface for Puppet

[huan]

When we are developing Wechaty with Puppet Providers, we will always face an error of instanceof mismatch, like

1. Wechaty Framework must keep only one Puppet instance wechaty#1930
2. How to develop and debug WecHaty locally wechaty#2024

According to https://stackoverflow.com/a/47116527/1123955, we can define an Interface for our AbstractPuppet class:

interface Puppet extends AbstractPuppet {
}

After that, we can always use the Interface of Puppet and never use instanceof again, for a better and a beautiful duck typing world.

[huan]

A workaround for now: wechaty/wechaty@2e951b7

[huan]

Related to wechaty/wechaty#1930