chore: remove legacy webL10n library and 1.2MB of dead assets (#5416)

Author: vyagh

index.html

@@ -79,7 +79,6 @@
             setTimeout(fixAutocompletePosition, 1000);
         });
     </script>
-    <script src="lib/webL10n.js" defer></script>
     <script src="lib/Tone.js" defer></script>
     <script src="lib/midi.js" defer></script>
     <script src="lib/jquery.ruler.js" defer></script>
@@ -109,7 +108,6 @@
 
     <script src="lib/acorn.min.js" defer></script>
 
-    <link rel="prefetch" type="application/l10n" href="./localization.ini" />
 
     <script data-main="js/loader" src="lib/require.js" defer></script>
     <link type="text/css" href="fonts/material-icons.css" rel="stylesheet">

js/utils/__tests__/utils.test.js

@@ -65,10 +65,6 @@ describe("Utility Functions (logic-only)", () => {
                     getContext: jest.fn(() => ({ measureText: () => ({ width: 42 }) }))
                 };
             }),
-            webL10n: {
-                get: jest.fn(str => str),
-                getLanguage: jest.fn(() => "en")
-            },
             body: { innerHTML: "" },
             createElement: jest.fn(() => {
                 return {

lib/sw.js

@@ -215,8 +215,8 @@ var urlsToCache = [
   'lib/reqwest.js',
   'lib/text.js',
   'lib/Tone.js',
-  'lib/tweenjs.min.js',
-  'lib/webL10n.js',
+  'lib/i18next.min.js',
+  'lib/i18nextHttpBackend.min.js',
 
   'css/activity.css',