docs: udpate usage section

packages/incremental-merkle-tree.sol/README.md

@@ -57,7 +57,51 @@ yarn add @zk-kit/incremental-merkle-tree.sol
 
 ## 📜 Usage
 
+```solidity
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.4;
 
+import "@zk-kit/incremental-merkle-tree.sol/contracts/IncrementalBinaryTree.sol";
+
+contract Test {
+    using IncrementalBinaryTree for IncrementalTreeData;
+
+    event TreeCreated(bytes32 id, uint8 depth);
+    event LeafInserted(bytes32 indexed treeId, uint256 leaf, uint256 root);
+    event LeafRemoved(bytes32 indexed treeId, uint256 leaf, uint256 root);
+
+    mapping(bytes32 => IncrementalTreeData) public trees;
+
+    function createTree(bytes32 _id, uint8 _depth) external {
+        require(trees[_id].depth == 0, "Test: tree already exists");
+
+        trees[_id].init(_depth, 0);
+
+        emit TreeCreated(_id, _depth);
+    }
+
+    function insertLeaf(bytes32 _treeId, uint256 _leaf) external {
+        require(trees[_treeId].depth != 0, "Test: tree does not exist");
+
+        trees[_treeId].insert(_leaf);
+
+        emit LeafInserted(_treeId, _leaf, trees[_treeId].root);
+    }
+
+    function removeLeaf(
+        bytes32 _treeId,
+        uint256 _leaf,
+        uint256[] memory _proofSiblings,
+        uint8[] memory _proofPathIndices
+    ) external {
+        require(trees[_treeId].depth != 0, "Test: tree does not exist");
+
+        trees[_treeId].remove(_leaf, _proofSiblings, _proofPathIndices);
+
+        emit LeafRemoved(_treeId, _leaf, trees[_treeId].root);
+    }
+}
+```
 
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