[Glitch] Play animated custom emoji on hover

Port 7de8c51873 to glitch-soc

app/javascript/flavours/glitch/packs/public.js

@@ -4,6 +4,7 @@ import ready from 'flavours/glitch/util/ready';
 function main() {
   const IntlMessageFormat = require('intl-messageformat').default;
   const { timeAgoString } = require('flavours/glitch/components/relative_timestamp');
+  const { delegate } = require('rails-ujs');
   const emojify = require('flavours/glitch/util/emoji').default;
   const { getLocale } = require('locales');
   const { messages } = getLocale();
@@ -23,6 +24,12 @@ function main() {
     }
   };
 
+  const getEmojiAnimationHandler = (swapTo) => {
+    return ({ target }) => {
+      target.src = target.getAttribute(swapTo);
+    };
+  };
+
   ready(() => {
     const locale = document.documentElement.lang;
 
@@ -94,6 +101,9 @@ function main() {
       document.head.appendChild(scrollbarWidthStyle);
       scrollbarWidthStyle.sheet.insertRule(`body.with-modals--active { margin-right: ${scrollbarWidth}px; }`, 0);
     }
+
+    delegate(document, '.custom-emoji', 'mouseover', getEmojiAnimationHandler('data-original'));
+    delegate(document, '.custom-emoji', 'mouseout', getEmojiAnimationHandler('data-static'));
   });
 }