Added missing files

frontend/utils/handlebars.ts

@@ -0,0 +1,26 @@
+import Handlebars from "handlebars"
+
+const createDocumentTemplateHandlebars = () => {
+  const instance = Handlebars.create()
+
+  instance.registerHelper("eq", (left, right) => left === right)
+  instance.registerHelper("ne", (left, right) => left !== right)
+  instance.registerHelper("gt", (left, right) => left > right)
+  instance.registerHelper("gte", (left, right) => left >= right)
+  instance.registerHelper("lt", (left, right) => left < right)
+  instance.registerHelper("lte", (left, right) => left <= right)
+  instance.registerHelper("and", (...args) => args.slice(0, -1).every(Boolean))
+  instance.registerHelper("or", (...args) => args.slice(0, -1).some(Boolean))
+  instance.registerHelper("not", (value) => !value)
+  instance.registerHelper("includes", (collection, value) => {
+    if (Array.isArray(collection) || typeof collection === 'string') {
+      return collection.includes(value)
+    }
+
+    return false
+  })
+
+  return instance
+}
+
+export const documentTemplateHandlebars = createDocumentTemplateHandlebars()