v0.8.0

Semver docker tags @max-lobur (#82)

what

• Use semver tags
• For event refs/tags/v1.2.3 this will push the following tags to the docker hub: 1.2.3, 1.2, latest

why

• To let users pin versions

notes

• release-branch workflow release-drafter must be given a PAT for this, otherwise tag event will not trigger the workflow
  https://github.com/cloudposse/github-actions-workflows/pull/49/files

references

https://github.com/docker/metadata-action#semver