handling uppercased 'Email' keyword
accept base64 encoded destination addresses

see https://assembly.com/formspree/bounties/8
accept base64 encoded address in _cc
a widget to help users base64encode their addresses
change all the example snippets with the b64-encoded address

see https://assembly.com/formspree/bounties/8#ad5dfd82-da2f-4564-a4d7-d9782e4bc302