Fix syntax highlighting unicode support (#475)

* convert BasicParser to a template

* fix syntax hightlighting with unicode characters

src/coders/xml.cpp

@@ -6,6 +6,7 @@
 #include <utility>
 
 #include "util/stringutil.hpp"
+#include "coders/BasicParser.hpp"
 
 using namespace xml;
 
@@ -191,7 +192,7 @@ inline bool is_xml_identifier_part(char c) {
 }
 
 namespace {
-class Parser : BasicParser {
+class Parser : BasicParser<char> {
     std::unique_ptr<Document> document;
 
     std::unique_ptr<Node> parseOpenTag() {