Browser extension that uses write-good

It would be great to have a Chrome or Firefox that uses write-good on any text input. This was suggested in #90, but wasn't taken up by any contributors. We'd be happy to look at a PR for this, for anyone who wants it.

Start by reviewing the related issue #90 and the existing write-good JavaScript entry points. Decide whether to target Chrome or Firefox first, then define how the extension reaches text inputs and how write-good results are shown; done means it works on text inputs in the chosen browser.

Written by the indexing model from the issue text.