feat(PDF):Add PDF viewer (#2730)

Display DICOM encapsulated PDF documents in a PDF viewer.
Addressed the remaining PR comments, and am merging this.

platform/viewer/cypress/integration/OHIFPdfDisplay.spec.js

@@ -0,0 +1,18 @@
+describe('OHIF PDF Display', function () {
+  before(() => {
+    cy.openStudyInViewer(
+      '2.25.317377619501274872606137091638706705333'
+    );
+  });
+
+  beforeEach(function () {
+    cy.resetViewport().wait(50);
+  });
+
+  it('checks if series thumbnails are being displayed', function () {
+    cy.get('[data-cy="study-browser-thumbnail"]')
+      .its('length')
+      .should('be.gt', 0);
+  });
+
+});