add ButtonBox component

src/components/ButtonBox.js

@@ -0,0 +1,62 @@
+import React, { Component } from 'react';
+import { Button, Row, Col } from 'reactstrap';
+import './ButtonBox.css';
+
+class ButtonBox extends Component {
+
+  constructor(props) {
+    super(props);
+  }
+
+  render() {
+    return (
+      <div className="button-box">
+        <Row>
+          <Col>
+            <Button
+              className="button"
+              block
+              size="lg"
+              color="success"
+              onClick={this.props.startTimer}
+              disabled={this.props.isStarted}
+            >
+              START
+            </Button>
+          </Col>
+        </Row>
+        <Row
+          className="top-margin"
+        >
+          <Col>
+            <Button
+              className="button"
+              block
+              color="danger"
+              size="lg"
+              onClick={this.props.stopTimer}
+              disabled={!this.props.isStarted}
+            >
+              STOP
+             </Button>
+          </Col>
+
+          <Col>
+              <Button
+                className="button"
+                block
+                color="secondary"
+                size="lg"
+                onClick={this.props.resetTimer}
+                disabled={this.props.isStarted}
+              >
+                RESET
+                </Button>
+            </Col>
+        </Row>
+      </div>
+        );
+      }
+    }
+    
+    export default ButtonBox;