fix(manifest): ensure manifest author is string, support object with email

[hellozzm]

Overview

Convert author field in manifest to string if it is an object, using the email property. Add test to verify author object is correctly converted to string in the generated manifest. Prevents invalid manifest format in Firefox and other browsers.

Manual Testing

Related Issue

This PR closes #1770

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[aiktb]

No browser other than Firefox needs the author. Some time ago Google removed this field from their MV3 manifest documentation reference.

As of May 2025, Chrome and the Chrome Web Store don't use this key.
Ref https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/author

I think these codes should be firefox only.

[hellozzm]

Yes, before making the revisions, I consulted the documentation:
https://developer.chrome.google.cn/docs/extensions/reference/manifest/author?hl=en

But perhaps this way of handling it can avoid reporting errors on Firefox

[Timeraa]

Does this also apply to stores like Opera, Edge Addons?

[hellozzm]

Does this also apply to stores like Opera, Edge Addons?

As shown in the attached image, the Opera browser extension also encounters the same issue, so the solution used for Firefox can also be applied to Opera. Edge, like Chrome, does not have this problem.