CI: add releasing helm chart

[zwpaper]

What type of PR is this?

/kind feature

What this PR does / why we need it:

release a helm chart when creating a tag/release as artifact, then we would host our helm chart repo on netlify page

Which issue(s) this PR fixes:

Fixes #607

Special notes for your reviewer:

this will create the helm chart as release artifact when creating v-prefix releases.

But I was thinking, the chart may change more frequently, maybe we should create some helm-chart-v-prefix releases?

Does this PR introduce a user-facing change?

release helm chart as artifact

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[Huang-Wei]

But I was thinking, the chart may change more frequently, maybe we should create some helm-chart-v-prefix releases?

Let's stick to tag name for now, and change if needed in the future.

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Huang-Wei, zwpaper

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