Update version in footer to 17 (#65)

Co-authored-by: Benjamin E. Coe <[email protected]>

Author: craigmorrison

_includes/footer.html

@@ -7,7 +7,7 @@
       <iframe src="https://ghbtns.com/github-btn.html?user=yargs&repo=yargs&type=star&count=true&size=large" frameborder="0" scrolling="0" width="160px" height="30px">&nbsp;</iframe>
       <a href="https://gitter.im/yargs/Lobby?utm_source=share-link&utm_medium=link&utm_campaign=share-link" target="_blank"><img src="https://img.shields.io/gitter/room/nwjs/nw.js.svg?maxAge=2592000" alt="gitter" /></a>
       <div class="footer-text">
-        Yargs · v5 · MIT License
+        Yargs · v17 · MIT License
       </div>
     </div>