Add Donate Cryptocurrent to OSGeo button

[Msmitherdc]

Code for CoinBase donations

<div>

<a class="donate-with-crypto"

href="​https://commerce.coinbase.com/checkout/0644fc63-4bce-4626-9686-6319e3cce9b3">

<span>Donate with Crypto</span>

</a> <script src="​https://commerce.coinbase.com/v1/checkout.js"> </script>

</div>

[cvvergara]

@Msmitherdc

Is this still in use?