missing a dist-tag for a mainnet-compatible agoric-sdk

[turadg]

Describe the bug

Developers need to be able to agoric install a version that matches Mainnet, rather than master.

To Reproduce

Try installing on of the dist-tags listed at npm info @agoric/zoe. It doesn't match Mainnet.

Expected behavior

One would expect agoric install agoric-upgrade-11 to work, but it has some problems related to npm package publishing and installation.

[mhofman]

There is now an agoric-upgrade-12 dist tag, and latest also points at the same. If there are issues with those packages, let's track in separate issues.