fix: parse json theme string for standalone tag (#1492)

Author: langhabel

src/standalone.tsx

@@ -32,7 +32,8 @@ function parseOptionsFromElement(element: Element) {
   const res = {};
   for (const attrName in attrMap) {
     const optionName = attrName.replace(/-(.)/g, (_, $1) => $1.toUpperCase());
-    res[optionName] = attrMap[attrName];
+    const optionValue = attrMap[attrName];
+    res[optionName] = attrName === 'theme' ? JSON.parse(optionValue) : optionValue;
     // TODO: normalize options
   }
   return res;