Fix mastodon >=3.2.1 delivery

[Skehmatics]

• Upgrade httpsig to fix https://github.com/go-fed/httpsig/issues/3
• Support https://www.ietf.org/archive/id/draft-ietf-httpbis-message-signatures-00.html

See: https://github.com/mastodon/mastodon/pull/14556 https://github.com/mastodon/mastodon/issues/15016

(Sorry for the mess, i am not a go dev :cry:)

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With :heart: from Vtopia

[yukimochi]

Thank you for your PR! 🎉

I'll check impact and new ietf drafts. I may add modify your PR for code integrity.

Please wait for review or merge.

[codecov-commenter]

Codecov Report

Base: 72.15% // Head: 72.15% // No change to project coverage :thumbsup:

Coverage data is based on head (10d1d4c) compared to base (353bd97). Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #52 +/- ## ======================================= Coverage 72.15% 72.15% ======================================= Files 15 15 Lines 1142 1142 ======================================= Hits 824 824 Misses 279 279 Partials 39 39 ``` | [Impacted Files](https://codecov.io/gh/yukimochi/Activity-Relay/pull/52?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Naoki+Kosaka) | Coverage Δ | | |---|---|---| | [deliver/sender.go](https://codecov.io/gh/yukimochi/Activity-Relay/pull/52/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Naoki+Kosaka#diff-ZGVsaXZlci9zZW5kZXIuZ28=) | `82.60% <100.00%> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Naoki+Kosaka). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Naoki+Kosaka)

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