Importing a helm chart version that isn't in the form x.y.z doesn't work even though it is valid SemVer-2

[TheGoldMonkey]

Description of the bug:

Importing a helm chart version that isn't in the form x.y.z doesn't work even though it is valid SemVer-2. I am trying to import a prerelease version which has the version 1.15.0-rc.0.
https://semver.org/#spec-item-9

Reproduction Steps:

Start a plain cdk8s project and run cdk8s import with the following cdk8s.yaml:

language: typescript
app: npx ts-node main.ts
imports:
  - helm:https://helm.cilium.io/[email protected]

Error Log:

Error: Invalid helm URL: helm:https://helm.cilium.io/[email protected]. Must match the format: 'helm:<repo-url>/<chart-name>@<chart-version>'.
    at extractHelmChartDetails (/root/.local/share/pnpm/global/5/.pnpm/[email protected]/node_modules/cdk8s-cli/lib/import/helm.js:116:19)
    at new ImportHelm (/root/.local/share/pnpm/global/5/.pnpm/[email protected]/node_modules/cdk8s-cli/lib/import/helm.js:47:53)
    at ImportHelm.fromSpec (/root/.local/share/pnpm/global/5/.pnpm/[email protected]/node_modules/cdk8s-cli/lib/import/helm.js:42:16)
    at matchImporter (/root/.local/share/pnpm/global/5/.pnpm/[email protected]/node_modules/cdk8s-cli/lib/import/dispatch.js:37:34)
    at async importDispatch (/root/.local/share/pnpm/global/5/.pnpm/[email protected]/node_modules/cdk8s-cli/lib/import/dispatch.js:13:26)
    at async Object.handler (/root/.local/share/pnpm/global/5/.pnpm/[email protected]/node_modules/cdk8s-cli/lib/cli/cmds/import.js:34:9)

Environment:

• Framework Version: 2.198.25
• OS: Ubuntu WSL2 Windows 11

Other:

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