Support Docker major / minor version tags

[ramonsmits]

The tags for the docker image are not following major/minor tagging:

https://hub.docker.com/r/dutchcoders/transfer.sh/tags

Latest release is v1.6.1

• Tag 1 should be set to tag 1.6.1
• Tag 1.6 should be set to tag 1.6.1
• Tag 1.5 should be set to tag 1.5.0

Optionally also support latest-release or something similar

[aspacca]

i'm find adding this tag and keeping them updated. thank you, @ramonsmits , very much for spotting out this! :)

can you file a PR to update the github workflow?

https://github.com/dutchcoders/transfer.sh/blob/main/.github/workflows/build-docker-images.yml

much appreciated!