Bindles must be signed before pushing

[adamreese]

Bindle had a breaking change forcing bindles to be signed before pushing to the server. deislabs/bindle#300

Bindle will return No signatures found on invoice. At least one signature is required

[radu-matei]

Spin currently uses Bindle v0.8, so if you want to use Bindle, make sure to use that and not a build from the latest Bindle main branch.

Keeping the issue open to track the breaking change in Bindle, thanks for filing.

[radu-matei]

Closing in favor of #689