Adding a snip toolbar button

Now that we have a draggable window and non-draggable menu buttons, let's add a button so that we can take a screenshot:

1. Update the App.js code and append a new button component with the icon value of camera and with the text Snip, as shown in the following example:

      <Navbar>
              <Navbar.Group align={Alignment.LEFT}>
                <Navbar.Heading>Electron Snip</Navbar.Heading>
                <Navbar.Divider />
                <Button className="bp3-minimal" icon="settings" 
                    text="Settings" />
                <Button className="bp3-minimal" icon="help" text="About" />
                <Button className="bp3-minimal" icon="camera" 
                                                      text=&quot...