Support a stable and a dev release channel in the CI/CD pipeline and the Helm charts about stunner

[davidkornel]

Major and minor tags should be stable.
Patch tags should be unstable tags.
Dev tags should be rebuilt every commit to follow the latest version of STUNner. There must be only one dev tag all time, delete the prev one before publishing the new dev release under l7mp.io.

Each chart is stored under l7mp.io repo. Users can reach the previous charts.

[davidkornel]

Fixed in #57
The original tag release is left as it was initially. A versioned and the latest charts are being created upon tagging.
With the new workflow upon every push, we create a new dev release for both the stunnerd docker image and helm chart.
In total we have the following resources:

• docker:
  • l7mp/stunnerd:latest
  • l7mp/stunnerd:<released-tag-version>
  • l7mp/stunnerd:dev
• helm:
  • stunner/stunner
  • stunner/stunner-dev

Potential problems/ideas for the feature:

• we might run out of the free 2k minutes
• we can skip building new dev versions if there was no code change (e.g. doc update)

IMO this issue can be closed and reopened if there is something else to do

[rg0now]

Thanks @davidkornel and @VidarHUN.