Template renderer class (#574)

* Convert handlebars.js to a class

* Move/rename function

* Update helper registration

* Rename helper functions

* Limit cache size

* Make render() async

* Rename and move

ext/bg/background.html

@@ -34,12 +34,12 @@
         <script src="/bg/js/dictionary-importer.js"></script>
         <script src="/bg/js/deinflector.js"></script>
         <script src="/bg/js/dictionary.js"></script>
-        <script src="/bg/js/handlebars.js"></script>
         <script src="/bg/js/json-schema.js"></script>
         <script src="/bg/js/media-utility.js"></script>
         <script src="/bg/js/options.js"></script>
         <script src="/bg/js/profile-conditions.js"></script>
         <script src="/bg/js/request.js"></script>
+        <script src="/bg/js/template-renderer.js"></script>
         <script src="/bg/js/text-source-map.js"></script>
         <script src="/bg/js/translator.js"></script>
         <script src="/bg/js/util.js"></script>

ext/bg/js/backend.js

@@ -27,10 +27,10 @@
  * JsonSchema
  * Mecab
  * ObjectPropertyAccessor
+ * TemplateRenderer
  * Translator
  * conditionsTestValue
  * dictTermsSort
- * handlebarsRenderDynamic
  * jp
  * optionsLoad
  * optionsSave
@@ -63,6 +63,7 @@ class Backend {
             audioSystem: this.audioSystem,
             renderTemplate: this._renderTemplate.bind(this)
         });
+        this._templateRenderer = new TemplateRenderer();
 
         const url = (typeof window === 'object' && window !== null ? window.location.href : '');
         this.optionsContext = {depth: 0, url};
@@ -1230,7 +1231,7 @@ class Backend {
     }
 
     async _renderTemplate(template, data) {
-        return handlebarsRenderDynamic(template, data);
+        return await this._templateRenderer.render(template, data);
     }
 
     _getTemplates(options) {