Fix/buffer undefined (Issue 3588)

[dxlin]

Context

For Issue 3588: Changes in webpack config may have caused Buffer to be undefined when using datasetToBlob function from dcmjs dependency.

Applying buffer definition under plugins appears to be a solution:
https://stackoverflow.com/questions/68707553/uncaught-referenceerror-buffer-is-not-defined

webpack/changelog-v5#10

Changes & Results

Added buffer definition under webpack config.plugins allows datasetToBlob to work again.

Testing

1. Start viewer
2. Select Water Phantom study (or any with CT and PT) in TMTV mode
3. Create "New Label" on right right
4. Select "Rectangle ROI Threshold Tool"
5. Create arbitrary rectangle in axial PT viewport
6. Click "Run"
7. Click "Create RT Report"

RT report should be prepared and prompt to save show up.

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: Windows 10
• [] Node version: 18.16.0
• [] Browser: Edge v115.0.1901.188

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[codecov]

Codecov Report

Merging #3590 (5d93fa0) into master (b55518e) will not change coverage.
Report is 2 commits behind head on master.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3590   +/-   ##
=======================================
  Coverage   42.58%   42.58%           
=======================================
  Files          80       80           
  Lines        1463     1463           
  Branches      340      340           
=======================================
  Hits          623      623           
  Misses        675      675           
  Partials      165      165           

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