Add included selector

[crutchcorn]

While working on a site that consumes this plugin (unicorn-utterances.com), I realized that it did not yet support SVGs or other image formats that I wanted to support (due to a lack of underlying class selectors for those images due to remarked-images not handling them.

I wanted a way to add those to the fray so I added an includedSelector to include those manually and added the CSS to enable this functionality

Example of it used in the gatsby-config.js:

{
    resolve: `gatsby-image-svg-version`,
    options: {
        includedSelector: '[src$=".svg"]'
    }
}

[JaeYeopHan]

sorry, too late! thanks :)