Scroll top fix @publiclab (publiclab#6944)

* Scroll button functionality

This hides the button when the user is at the top of the webpage but reveal the button when the user scrolls.

* public lab scroll-to-top #issue 6435

This consists of a function that hides the to-top button on the page and reveal it when the user scrolls

* indent fixed

This is the same scroll-func.js file but with the indentations in a more orderly manner.

scroll-func.js

@@ -0,0 +1,10 @@
+let scrollBtn = document.querySelector(".back-to-top");
+window.addEventListener("scroll", function(){
+      let position = window.scrollY;
+      if(position < 200){
+      scrollBtn.style.opacity = "0";
+    }
+      else{
+            scrollBtn.style.opacity = "1";
+      }
+})