doc: update sidebar

Author: ObservedObserver

docs/_sidebar.md

@@ -1,6 +1,20 @@
 + APIs
     + [Clusters](./apis/clusters.md)
+        + [HDBSCAN](./apis/clusters/hdbscan.md)
+        + [K-Means](./apis/clusters/kmeans.md)
+        + [K-Means++](./apis/clusters/kmeansPlusPlus.md)
+        + [Mean Shift](./apis/clusters/meanShift.md)
+        + [OPTICS](./apis/clusters/optics.md)
+    
     + [Ensemble](./apis/ensemble.md)
+        + [Isolation Forest](./apis/ensemble/iforest.md)
+    
     + [Neighbors](./apis/neighbors.md)
+        + [KNN](./apis/neighbors/knn.md)
+    
     + [Tree](./apis/tree/index.md)
+        + [Decision Tree Classifier](./apis/tree/decisionTreeClassifier.md)
+        + [Decision Tree Regressor](./apis/tree/decisionTreeRegressor.md)
+    
     + [Linear](./apis/linear/index.md)
+        + [Linear Regression](./apis/linear/linearRegression.md)