Save and restore scroll position

* This is a big deal when typing thoughts that are over a page long, it will jump you to the bottom of the input box every time and it's a little jarring.

main/templates/whispermaphone/post.html

@@ -40,11 +40,15 @@
     const textExtEl = document.getElementById("id_extended_text");
 
     function updateBoxHeight(box) {
+        // Save scroll position
+        const scrollY = window.scrollY;
         //style.height doesn't include padding, .scrollHeight does
         box.style.height = "auto";
         // Set overflow hidden to ensure scrollbars aren't shown, since they change the width and thus the height
         box.style.overflow = "hidden";
         box.style.height = box.scrollHeight + "px";
+        //Restore scroll position
+        window.scrollTo(0, scrollY);
     }
 
     // If we're handling maxlength in JS, then having the maxlength attribute is annoying