Adds log for written files

[dominicbarnes]

This adds a "write" event internally that is trigged after writing a file. The first use-case is obvious, it shows when the entry file was successfully written. Now that external source-maps are a thing, this will now show when that write is successful too.

Current

$ duo index.js

     building : index.js
        using : compatibility
        using : stoj
        built : index.js

Now

$ duo index.js

       building : index.js
          using : compatibility
          using : stoj
          built : index.js
        written : index.js

Now (with external source-map)

$ duo --external-source-maps index.js

     building : index.js
        using : compatibility
        using : stoj
        built : index.js
      written : index.js
      written : index.js.map

[stephenmathieson]

shouldn't it be "wrote"?

[dominicbarnes]

@duojs/owners What would you guys think about using green to bring emphasis to the "wrote" event?

It's still using cyan like most everything else. But since this is a successful operation, I thought it might be appropriate to use a "successful-looking" color.

[matthewmueller]

oops, sorry late response. +1 to green :-)

[dominicbarnes]

@matthewmueller bbaabbef14e635e13fdc436557def36e2926cfad