Parser: Add category to tagfinder to replace it with an empty str

parser.cpp

@@ -120,7 +120,7 @@ std::string Parser::parse(const PageDao &pagedao, UrlProvider &provider, std::st
 {
 	std::string result;
 	// we don't care about commands, but we nevertheless replace them with empty strings
-	std::regex tagfinder(R"(\[(b|i|u|li||ul|ol|link|wikilink|h\d|cmd:rename|cmd:redirect)*?\]((\s|\S)*?)\[/\1])");
+	std::regex tagfinder(R"(\[(b|i|u|li||ul|ol|link|wikilink|h\d|cmd:rename|cmd:redirect|category)*?\]((\s|\S)*?)\[/\1])");
 	result = utils::regex_callback_replacer(tagfinder, content, [&](std::smatch &match) {
 		std::string tag = match.str(1);
 		std::string content = match.str(2);