Resolve "[FIXME] large conda envs cannot be shared in Gitlab"

Closes #2

Tagging as draft to start a discussion, and iron out the wrinkles.

This MR combines the build and publish job together. When archives exceed a certain size they cannot be cached as job artifacts, therefore making publication impossible.

Based on what we discussed with @otto, I'd like to propose a workflow that allows:

• building and publishing automatically on tagged commits.
• allowing manual build and publication on regular commits.

To support local development and testing, a dev should run conda-dist manually. See for example: https://gitlab.wikimedia.org/repos/research/knowledge-gaps/-/blob/5-add-ci-integration-package-conda-env-wip/Makefile#L50