Oh hi!
When you install this site to your phone's home screen, it creates a new item in your native 'Share' menu that, when clicked, redirects you to the 'Add to Pinboard- with tags' window. Pretty neat, huh?
Want to make it your own? Remix this app on Glitch (find the link in that fish button at the top of the page) and customize it however you want. Maybe you want to use a different URL from Pinboard because you don't care to see your tags? Change that in server.js, in the 'share-target' route.