(volume-viewport): call render for the scroll to take effect

[minimal-scouser]

Context

calling scroll on a volume viewport does not actually scroll the viewport. it sets camera properties (focal point and position) but it needs a render to get those committed to viewport.

Changes & Results

call render method inside the scroll method of baseVolumeViewport

Testing

Checklist

PR

• [] My Pull Request title is descriptive, accurate and follows the
  semantic-release format and guidelines.

Code

• [] My code has been well-documented (function documentation, inline comments,
  etc.)

Public Documentation Updates

• [] The documentation page has been updated as necessary for any public API
  additions or removals.

Tested Environment

• [] "OS:
• [] "Node version:
• [] "Browser:

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