fix: escape quotes failing when value is not a string

addresses resend/react-email#1632

Author: gabrielmfern

src/utils.ts

@@ -4,7 +4,7 @@ import { RendererObject } from "marked";
 import { styles } from "./styles";
 
 function escapeQuotes(value: string) {
-  if (value.includes('"')) {
+  if (typeof value === 'string' && value.includes('"')) {
     return value.replace(/"/g, "'");
   }
   return value;