fix(invert): Resetting the stack viewport properties should revert to the image's original invert setting

[jbocce]

Context

Fixes #764

Possibly addresses https://community.ohif.org/t/images-gets-inverted-when-resetting-zoom/1000

Changes & Results

Introduced an instance variable initialInvert to store the original invert for the image displayed.

Testing

Follow the instructions for #764.

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.)

• I have run the yarn build:update-api to update the API documentation, and have
  committed the changes to this PR. (Read more here https://www.cornerstonejs.org/docs/contribute/update-api)

Public Documentation Updates

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

Tested Environment

• "OS: Windows 11
• "Node version: 16.14.0
• "Browser: Chrome 117.0.5938.89

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[sedghi]

Thanks