update README.md to explain how to use the new version

Author: akalp

README.md

@@ -1,3 +1,59 @@
+### How to use bs5-nav-tree v0.2.1
+#### Initializing the tree
+1. Make sure you have a list object with id "nav-tree" like ``<ul id="nav-tree"></ul>`` and, all list items must have its own id like ``<li id="li1"></li>``. If you have speacial list item or link add 'extra' class to exulude it. 
+   
+   For example:
+    ```html
+    <ul id="nav-tree">
+      <li id="li8">
+        <a>
+          Collapse 3
+        </a>
+        <ul>
+          <li id="li9">
+            <a href="#">
+              Link 4
+            </a>
+          </li>
+          <li id="li10">
+            <a href="#">
+              Link 5
+            </a>
+          </li>
+        </ul>
+      </li>
+    </ul>
+    ```
+2. Add this to your js file:
+   ```js
+   const nav = new NavTree(
+     {
+        selector: "#nav-tree",
+        searchable: false, // default
+        showEmptyGroups: false, // default
+
+        groupOpenIconClass: "fas", // default
+        groupOpenIcon: "fa-chevron-down", // default
+
+        groupCloseIconClass: "fas", // default
+        groupCloseIcon: "fa-chevron-right", // default
+
+        linkIconClass: "fas", // default
+        linkIcon: "fa-link", // default
+
+        iconWidth: "",  // default
+
+        searchPlaceholderText: "Search", // default
+      }
+   );
+   ```
+
+#### Updating the tree
+```js
+nav.update(menu_html);
+```
+
+
 ### How to use bs5-nav-tree v0.2
 #### Initializing the tree
 1. Make sure you have a list object with id "nav-tree" like ``<ul id="nav-tree"></ul>`` and, all list items must have its own id like ``<li id="li1"></li>``.  If you want to search on tree add "data-searchable" attribute to the list, and if you want to show empty groups after search add "data-show-empty-groups" attribute to the list.