fix(contentful): reenable support for gif images

[axe312ger]

With the rewrite to gatsby-plugin-image and Gatsby v3 we are more strict when calling the Contentful Images API

Unfortunately, as we now always pass a image format. This broke gif support:

Before we called like this: https://images.ctfassets.net/k8iqpp6u0ior/2uMYE0Za3MOF9eVrx7eyiW/ace850f7bf6cbf52e3922b5db8379b7a/gatsby-monogram-animated.gif?w=150

Now we call like this: https://images.ctfassets.net/k8iqpp6u0ior/2uMYE0Za3MOF9eVrx7eyiW/ace850f7bf6cbf52e3922b5db8379b7a/gatsby-monogram-animated.gif?w=150&fm=gif

Which unfortunately fails:

{
  "sys": {
    "type": "Error",
    "id": "ParameterValuesNotAllowed",
    "details": {
      "error": "required fm: 'gif' valid transformation: False"
    }
  }
}

Good news: This is a configuration bug in the Contentful API and will be fixed very very soon.

This patch allows gifs now as image format as well :)

[axe312ger]

Will remove the draft as soon the API fix is deployed.

[axe312ger]

The fix is rolled out :)