Skip VS15 (Emoji textual presentation). (#8553)

Mastodon converts all Emoji to images, whether they have a VS15 after
them or not, but leaves the VS15 in the string, which is displayed as
a black box in Safari.

app/javascript/mastodon/features/emoji/emoji.js

@@ -62,6 +62,10 @@ const emojify = (str, customEmojis = {}) => {
       const title = shortCode ? `:${shortCode}:` : '';
       replacement = `<img draggable="false" class="emojione" alt="${match}" title="${title}" src="${assetHost}/emoji/${filename}.svg" />`;
       rend = i + match.length;
+      // If the matched character was followed by VS15 (for selecting text presentation), skip it.
+      if (str.codePointAt(rend) === 65038) {
+        rend += 1;
+      }
     }
     rtn += str.slice(0, i) + replacement;
     str = str.slice(rend);