Allow for array specification for elements accepting multiple values.

[Clockwork-Muse]

Azure DevOps pipeline definitions (and potentially GitHub Actions as well, but I haven't done much with them) allows for inputs to tasks and template parameters to be arrays.

Where possible, please consider switching to using this functionality, instead of whatever other style is used currently. It would mean the definition could look like this:

- task: DevcontainersCi@0
  inputs:
    imageName: $(RegistryImage)
    # Currently imageTag is a comma separated list
    imageTag:
      - $(VersionTag)
      - ${{ if parameters.pushLatest }}:
        - latest
    push: filter
    sourceBranchFilterForPush: refs/heads/main
    # Currently cacheFrom requires a multi-line definition
    cacheFrom:
      - $(RegistryImage):latest
      - $(RegistryImage):$(VersionTag)
    noCache: ${{ parameters.noCache }}

... instead of:

- task: DevcontainersCi@0
  inputs:
    imageName: $(RegistryImage)
    ${{ if parameters.pushLatest }}:
      imageTag: $(VersionTag),latest
    ${{ else }}:
      imageTag: $(VersionTag)
    push: filter
    sourceBranchFilterForPush: refs/heads/main
    # To get multiple items
    cacheFrom: |
      $(RegistryImage):latest
      $(RegistryImage):$(VersionTag)
    noCache: ${{ parameters.noCache }}

---

As an aside, there appears to be **no** documentation around how to pass multiple elements to `cacheFrom`. It doesn't complain if you pass a comma-separated list (somehow), but it only generates a single `--cache-from` argument, instead of a separate one for each image.

[bamurtaugh]

Thank you for filing @Clockwork-Muse. cc @stuartleeks for thoughts