Update docs

contracts/mocks/EnumerableSetMock.sol

@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity >=0.6.0 <0.8.0;
+
+import "../utils/EnumerableSet.sol";
+
+// Bytes32Set
+contract EnumerableBytes32SetMock {
+    using EnumerableSet for EnumerableSet.Bytes32Set;
+
+    event OperationResult(bool result);
+
+    EnumerableSet.Bytes32Set private _set;
+
+    function contains(bytes32 value) public view returns (bool) {
+        return _set.contains(value);
+    }
+
+    function add(bytes32 value) public {
+        bool result = _set.add(value);
+        emit OperationResult(result);
+    }
+
+    function remove(bytes32 value) public {
+        bool result = _set.remove(value);
+        emit OperationResult(result);
+    }
+
+    function length() public view returns (uint256) {
+        return _set.length();
+    }
+
+    function at(uint256 index) public view returns (bytes32) {
+        return _set.at(index);
+    }
+}
+
+// AddressSet
+contract EnumerableAddressSetMock {
+    using EnumerableSet for EnumerableSet.AddressSet;
+
+    event OperationResult(bool result);
+
+    EnumerableSet.AddressSet private _set;
+
+    function contains(address value) public view returns (bool) {
+        return _set.contains(value);
+    }
+
+    function add(address value) public {
+        bool result = _set.add(value);
+        emit OperationResult(result);
+    }
+
+    function remove(address value) public {
+        bool result = _set.remove(value);
+        emit OperationResult(result);
+    }
+
+    function length() public view returns (uint256) {
+        return _set.length();
+    }
+
+    function at(uint256 index) public view returns (address) {
+        return _set.at(index);
+    }
+}
+
+// UintSet
+contract EnumerableUintSetMock {
+    using EnumerableSet for EnumerableSet.UintSet;
+
+    event OperationResult(bool result);
+
+    EnumerableSet.UintSet private _set;
+
+    function contains(uint256 value) public view returns (bool) {
+        return _set.contains(value);
+    }
+
+    function add(uint256 value) public {
+        bool result = _set.add(value);
+        emit OperationResult(result);
+    }
+
+    function remove(uint256 value) public {
+        bool result = _set.remove(value);
+        emit OperationResult(result);
+    }
+
+    function length() public view returns (uint256) {
+        return _set.length();
+    }
+
+    function at(uint256 index) public view returns (uint256) {
+        return _set.at(index);
+    }
+}