Prop definitions

We should define properties in the props property so that they're as detailed as possible by specifying their types (at a minimum). It is only okay to not have detailed definitions when you're prototyping. For example, this is considered bad practice:

props: ['message']

This should be written as follows:

props: {
  message: String
}

Or, even better, it should be written as follows:

props: {
  message: {
    type: String,
    required: false,
    validator (value) { ... }
  }
}