fix HTML formatting in timeline diagrams

cypress/integration/rendering/timeline.spec.ts

@@ -225,4 +225,18 @@ timeline
       {}
     );
   });
+  it('13: should render markdown htmlLabels', () => {
+    const timelineCode = `%%{init: { 'logLevel': 'debug', 'theme': 'forest' } }%%
+    timeline
+    title Timeline of Industrial Revolution
+    section 17th-20th century
+        Industry 1.0 : Machinery, Water power, Steam <br>power
+        Industry 2.0 : Electricity, <strong>Internal combustion engine </strong>, Mass production
+        Industry 3.0 : Electronics, Computers, Automation
+    section 21st century
+        Industry 4.0 : Internet, Robotics, Internet of Things
+        Industry 5.0 : Artificial intelligence, Big data, 3D printing
+      `;
+    imgSnapshotTest(timelineCode);
+  });
 });