fix: use semantic release GH actions

[cjumel]

Description

This is another attempt at fixing the release workflow with semantic release. It:

• removes semantic-release as a package dev dependency to use the dedicated GH action
• use the full workflow example for the whole release cycle (the publish to pypi part was missing until there)
• change the GitHub token variable name to use something re-usable accross packages

Checklist

• I have run the tests locally with make install-dev and make test
• I have updated the README.md if my changes affected it
• I have updated the package version in linkup/_version.py and pyproject.toml if I plan on creating a new release