feat: add support for pushing charts to oci (ghcr)

[dmccaffery]

Add support for pushing charts to GHCR in addition to releases.

As of helm v3.8.0, oci support is now generally available.

Dependency: helm/chart-releaser#183

[acuD1]

This PR (#143) should solve this issue. Just need to add --skip-upload.

There is a snippet from my CI workflow:

      - name: Run chart-releaser
        uses: acuD1/chart-releaser-action@main
        with:
          skip_upload: true
        env:
          CR_TOKEN: "${{ secrets.CI_TOKEN }}"

      - name: Login to GHCR
        uses: acuD1/login-action@master
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.CI_TOKEN }}
          
      - name: Push Charts to GHCR
        run: |
          for pkg in .cr-release-packages/*; do
            if [ -z "${pkg:-}" ]; then
              break
            fi
            helm push "${pkg}" oci://ghcr.io/${{ env.REPOSITORY_OWNER }}/${{ env.REPOSITORY }}
          done

Until it's fully released (#186) you can use my branch.