Restore mobile CTA button

whoops!

Author: jboolean

frontend/src/screens/App/screens/Welcome/index.tsx

@@ -52,6 +52,19 @@ export default function Welcome({
             <br />
             <strong>Zoom in! Every dot&nbsp;is&nbsp;a&nbsp;photo.</strong>
           </p>
+          <div
+            className={classNames(
+              stylesheet.buttonContainer,
+              stylesheet.mobileButton,
+              stylesheet.mobileOnly
+            )}
+            onClick={handleClose}
+          >
+            <Button buttonStyle="primary" className={stylesheet.explore}>
+              Start Exploring
+            </Button>
+          </div>
+
           <hr />
           <p className={stylesheet.finePrint}>
             The photos on this site were retrieved from the NYC Department of