docs: addPasskey broken link

[avarobinson]

Is this a request for new documentation or updates to existing documentation
addPasskey broken link: https://accountkit.alchemy.com/packages/aa-alchemy/signer/addPasskey#addpasskey

If existing documentation, a clear summary of what needs to be changed
A clear and concise description of what documentation should be changed, and a link to the resource that needs the update.

If new documentation, a clear summary of what needs to be added
A clear and concise description of what documentation should be added.

Additional context
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