Document how to contribute to Who Goes First in the site footer.

[tswast]

Want:

• [x] File feedback.
• [x] File issues.
• [x] Translate the page.
• [x] Fork and contribute.
• [x] Donate money.
• [ ] Discuss.
• [x] Add a new card.

[tswast]

I think we should use the proper metadata to tag image licenses. Example from https://pixabay.com/en/laurel-wreath-award-wreath-winning-30482/ using https://schema.org/ImageObject.

<div id="media_container" class="" itemscope="" itemtype="schema.org/ImageObject">
                <meta itemprop="license" content="https://creativecommons.org/licenses/publicdomain/">
                <img itemprop="contentURL" src="/static/uploads/photo/2012/04/12/20/17/laurel-wreath-30482_640.png" alt="Laurel Wreath, Award, Wreath, Winning, Leaves">
</div>
<a style="position:absolute;left:-9999px" rel="license" about="/static/uploads/photo/2012/04/12/20/17/laurel-wreath-30482_640.png" href="https://creativecommons.org/licenses/publicdomain/">Public Domain</a>

I didn't see the "about" option on https://creativecommons.org/choose/ but maybe that could be useful for the "about this card" page where I don't necessarily want to display the image again?

[tswast]

We should definitely include a badge for our Gratipay. https://gratipay.com/Who-Goes-First/

Example:

[![Gratipay Team](https://img.shields.io/gratipay/team/Who-Goes-First.svg?maxAge=2592000)](https://gratipay.com/Who-Goes-First/)

[tswast]

This was finished in https://github.com/whogoesfirst/who-goes-first/pull/64.

I didn't add a "discuss Who Goes First" link, but social media / Reddit can be a separate thing.