Signs the plugin in <dir> (default: cwd) and writes
priv/mob_plugin.sig. The signature covers the loaded manifest
plus SHA-256 hashes of every file the manifest references.
mix mob.plugin.sign [--plugin <dir>]Reads the private key for the plugin's :name from
~/.mob/keys/<name>.priv. Run mix mob.plugin.keygen first if you
haven't already.
After signing, the printed fingerprint can be shared with host
operators so they can run mix mob.plugin.trust <name> to record
trust in their mob.exs.