chore: cleanup dcmjs imports

* Update imports in /platform

* Update dcmjs imports in /extentions

extensions/dicom-html/src/DicomHtmlViewport.js

@@ -1,6 +1,6 @@
 import React, { Component } from 'react';
 import PropTypes from 'prop-types';
-import * as dcmjs from 'dcmjs';
+import dcmjs from 'dcmjs';
 import TypedArrayProp from './TypedArrayProp';
 
 import './DicomHtmlViewport.css';

extensions/dicom-rt/src/loadRTStruct.js

@@ -1,5 +1,5 @@
 import OHIF from '@ohif/core';
-import * as dcmjs from 'dcmjs';
+import dcmjs from 'dcmjs';
 import cornerstone from 'cornerstone-core';
 import cornerstoneTools from 'cornerstone-tools';
 import transformPointsToImagePlane from './utils/transformPointsToImagePlane';

extensions/dicom-segmentation/src/loadSegmentation.js

@@ -1,5 +1,5 @@
 import OHIF from '@ohif/core';
-import * as dcmjs from 'dcmjs';
+import dcmjs from 'dcmjs';
 import cornerstone from 'cornerstone-core';
 import cornerstoneTools from 'cornerstone-tools';