Add Forward Email to email service providers

[titanism]

Disclosure: We are the maintainers and owners of this business, which has been around since 2017 and is the only 100% open-source email service.

Changes proposed in this PR:

Hi there! :wave: We have added our service Forward Email to the list of email service providers. It supports both SMTP, IMAP, POP3, API, webhooks, catch-alls, regular expressions, aliases, and email forwarding. We've been around since 2017 and support ~250,000 domain names right now, reject 30M+ spam emails daily, and deliver 1M+ emails daily. To highlight a few users, we're used by The National Association for Amateur Radio (ARRL), Disney Ad Sales, Google's Flutter dev team, and Tufts University.

Unlike Proton Mail ¹, Skiff ², and Tuta ³, we are actually 100% open-source on GitHub (@forwardemail is our org).

Happy to make any changes to the docs as necessary for this PR to get merged! Let us know if you have any questions or if we can clarify anything else further. Our FAQ is pretty extensive.

To keep your site Privacy Guides tidy and optimized, we also ran svgo to compress the svg icon files we added in this PR:

❯ svgo --multipass forward-email.svg -o forward-email.svg

forward-email.svg:
Done in 57 ms!
23.645 KiB - 58% = 9.932 KiB

P.S. Happy holidays and happy new year 🎉

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