feat: add onProgress hook

[benallfree]

@crutchcorn I'm curious to see what you think of this PR.

It adds an onProgress hook and makes it available to be called from custom action handlers like this:

const myCustomAction =  async (answers, config, plop)=>{
   const { onProgress } = config
   onProgress(`Starting action`)
   return new Promise(resolve=>{
      setTimeout(()=>resolve(`Finished action`),1000)
   }
}