tag v3.10.0: git.sr.ht deploy keys

Manage a git repository's deploy keys from the repository actions menu
(owner-only), alongside ACLs: list keys with their fingerprint, comment,
and read-only / read-write access; add an SSH public key; and delete a key
behind a confirmation. Wraps git.sr.ht's createDeployKey / deleteDeployKey
and Repository.deployKeys.

Verified live against the ~hutch account. createDeployKey's response omits
the key's fields (empty access), so the create selects only rid and the
list is reloaded rather than decoding a partial key.