Update docs

docs/tutorial/activate-your-webcam.md

         );
     }
 
-    const tracker = AR.Tracker.ImageTracker();
+    const tracker = AR.Tracker.Image();
     await tracker.database.add([{
         name: 'my-reference-image',
         image: document.getElementById('my-reference-image')
         );
     }
 
-    const tracker = AR.Tracker.ImageTracker();
+    const tracker = AR.Tracker.Image();
     await tracker.database.add([{
         name: 'my-reference-image',
         image: document.getElementById('my-reference-image')
         );
     }
 
-    const tracker = AR.Tracker.ImageTracker();
+    const tracker = AR.Tracker.Image();
     await tracker.database.add([{
         name: 'my-reference-image',
         image: document.getElementById('my-reference-image')
         );
     }
 
-    const tracker = AR.Tracker.ImageTracker();
+    const tracker = AR.Tracker.Image();
     await tracker.database.add([{
         name: 'my-reference-image',
         image: document.getElementById('my-reference-image')

docs/tutorial/next-steps.md

 
     AR.Settings.powerPreference = 'low-power'; // OPTIONAL
 
-    const tracker = AR.Tracker.ImageTracker();
+    const tracker = AR.Tracker.Image();
     await tracker.database.add([{
         name: 'my-reference-image',
         image: document.getElementById('my-reference-image')

docs/tutorial/set-up-the-session.md

             );
         }
 
-        const tracker = AR.Tracker.ImageTracker();
+        const tracker = AR.Tracker.Image();
         await tracker.database.add([{
             name: 'my-reference-image',
             image: document.getElementById('my-reference-image')
             );
         }
 
-        const tracker = AR.Tracker.ImageTracker();
+        const tracker = AR.Tracker.Image();
         await tracker.database.add([{
             name: 'my-reference-image',
             image: document.getElementById('my-reference-image')
             );
         }
 
-        const tracker = AR.Tracker.ImageTracker();
+        const tracker = AR.Tracker.Image();
         await tracker.database.add([{
             name: 'my-reference-image',
             image: document.getElementById('my-reference-image')
         );
     }
 
-    const tracker = AR.Tracker.ImageTracker();
+    const tracker = AR.Tracker.Image();
     await tracker.database.add([{
         name: 'my-reference-image',
         image: document.getElementById('my-reference-image')

docs/tutorial/set-up-the-tracker.md

             );
         }
 
-        const tracker = AR.Tracker.ImageTracker();
+        const tracker = AR.Tracker.Image();
     }
     catch(error) {
         alert(error.message);
             );
         }
 
-        const tracker = AR.Tracker.ImageTracker();
+        const tracker = AR.Tracker.Image();
         await tracker.database.add([{
             name: 'my-reference-image',
             image: document.getElementById('my-reference-image')