Shared content between index.html and donations.html needs to be updated in two places

[trichoplax]

I haven't filled out the standard bug sections as this is not really a bug, just a "bug waiting to happen" - I wasn't sure if "bug" was the best category to pick but it didn't seem like a feature request either, as it makes no difference to the end user.

Nothing is wrong at the moment, but having shared content duplicated in these two files introduces the risk of updating one and forgetting to update the other.