docs(gatsby-source-contentful): Add info to readme on use with new image plugin (#29297)
docs(gatsby-source-contentful): Add info to readme on use with new image plugin (#29297)

* docs(gatsby-source-contentful): Add info to readme on use with new image plugin

* Apply suggestions from code review

Co-authored-by: LB <8468275f0d120527324004754c3d088324306866@gatsbyjs.com>

* Add link to plugin

Co-authored-by: LB <8468275f0d120527324004754c3d088324306866@gatsbyjs.com>
gatsbyjs/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby