I tried adding this myself but I got an unspecified error message. This is the Spanish Wiktionary to search for Spanish lemmas.
{
"dictName": "Wiktionary (es)",
"windowUrl": "https://es.m.wiktionary.org/wiki/<word>#Español",
"windowUrlMatch": "wiki/([^&]+)",
"resources": {
"styles": ["wiktionary.less"]
}
}