Tweaked scrollToPostIndex logic

The old behaviour would scroll the post anchor to the midline, but
this was inferior UX for long posts since the top half of the
screen is essentially stuff you didn't want to see.

The new logic is as follows:
- If the target post is smaller than the browser viewport, it will
  scroll in such a way that the entire post is vertically centered
  (post midline matching viewport midline)
- If the target post is larger than the browser viewport, it will
  scroll in such a way that the top of the post is located just
  under the navbar, maximizing the target post's content.
- Updated themes to relocate their anchors to in between posts

package.json

@@ -53,8 +53,8 @@
     "nodebb-plugin-spam-be-gone": "0.4.6",
     "nodebb-rewards-essentials": "0.0.8",
     "nodebb-theme-lavender": "3.0.9",
-    "nodebb-theme-persona": "4.0.112",
-    "nodebb-theme-vanilla": "5.0.59",
+    "nodebb-theme-persona": "4.0.113",
+    "nodebb-theme-vanilla": "5.0.60",
     "nodebb-widget-essentials": "2.0.8",
     "nodemailer": "2.0.0",
     "nodemailer-sendmail-transport": "1.0.0",

public/src/modules/navigator.js

@@ -190,7 +190,12 @@ define('navigator', ['forum/pagination', 'components'], function(pagination, com
 	};
 
 	navigator.scrollToPostIndex = function(postIndex, highlight, duration) {
-		var scrollTo = components.get('post/anchor', postIndex);
+		var scrollTo = components.get('post/anchor', postIndex),
+			postEl = components.get('post', 'index', postIndex),
+			postHeight = postEl.height(),
+			viewportHeight = $(window).height(),
+			navbarHeight = components.get('navbar').height();
+
 
 		if (!scrollTo.length) {
 			navigator.scrollActive = false;
@@ -202,7 +207,12 @@ define('navigator', ['forum/pagination', 'components'], function(pagination, com
 		var done = false;
 
 		function animateScroll() {
-			var scrollTop = (scrollTo.offset().top - ($(window).height() / 2)) + 'px';
+			var scrollTop = 0;
+			if (postHeight < viewportHeight) {
+				scrollTop = (scrollTo.offset().top - (viewportHeight / 2) + (postHeight / 2)) + 'px';
+			} else {
+				scrollTop = scrollTo.offset().top - navbarHeight;
+			}
 
 			$('html, body').animate({
 				scrollTop: scrollTop