Proposal: Publish command

The main purpose of the `publish` command is to create a release. It would executes the following sub commands:

1. check local repository is clean (no uncommitted files) and all commits have been pushed.
1. prompt user for input values (see below)
1. ~create a git tag with the following parameters:~
- tag: semver based on the latest release fetched from the server + 1. A flag determines whether +1 means MAJOR, MINOR or PATCH
- object: the latest local commit SHA.
1. create a github release, with the following parameters:
- tag_name: the tag previously created
- name: prompt user
- body: prompt user
- draft: false
- prerelease: prompt user
1. Optional: *pull* tags
1. Update version in manifest
1. Register github repo to OW hub. If already registered, this is a noop.

Note that 3, 4 and 7 are server-side commands run by OW actions. This actions should probably be implemented in a different github project.